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September 2023 Weather Recap: 2nd Rainiest September on Record

  Sept 29 2023 rainstorm_map1-abc-ml-230929_1695989164289_hpEmbed_16x9

After a very warm and dry start, September 2023 ended cool and very wet.  The six-day period Sept. 3-8 all had highs of 88° or hotter, with an average high of 91° (eleven degrees above average).  Then the eight-day period Sept. 23-30 all had highs of 66° or cooler, with an average high of 64° (eight degrees below average).  Temperature-wise, the two periods balanced each other out and the month ended up with a close to average temperature (+0.2 degrees above average). 

 

After having no days in the 90s in August, September had four, the most in September since there were six in Sept. 2015.  The four days in the 90s were consecutive, making this the only heat wave of the year.  And with highs of 93°, Sept. 6 and 7 tied July 5 for hottest reading of the year.  (9/6, with a high/low of 93°/77° had the hottest mean temperature of the year.) 

 

Despite there being no measurable rain in the first week of the month, September 2023 ended up being the second rainiest September on record with 14.25" measured  (September 1882 had 16.85") - and the fourth wettest of any month.  More than half of the rain (8.90") fell in the last eight days of the month. (This amount alone would have made it the 10th wettest September.)

 

Chart - 5 rainiest months on record

 

Five days had more than an inch of rain (and another had 0.96"), the most in one month since August 2011 which had six.   The rainstorm of 9/29 produced 5.48" of rain (much of it in a 3-hour period), the ninth greatest amount to fall on a calendar date.  Tropical storm Ophelia impacted NYC's weather for four days (9/22-9/25) and produced 3.00" of rain, close to what fell in just two hours on 9/29.

 Chart - Sept 2023 Daily Rainfalls of 1 Inch or More

The last 16 days of the month all had below average mean temperatures, the longest below average streak since April 2020, which also had a 16-day streak in the month's last 16 days (a streak of 22 days, occurred in March 2018).  Additionally, the last eight days all had highs in the 60s, the longest such streak in September in the years since 1960 (the coolest reading of the month, 50°, was reported on 9/27).  For the entire month there were 10 days with sub-70 highs, which was the most in September since 2006.  

 

In total, there were 12 days with highs in the 90s in 2023, the fewest since 2014, which had eight.  The last time a summer had its hottest reading at 93° or cooler was in 2014 when it was 92°.

 

Of the 23 years in which August had no readings in the 90s, September 2023 had the second most highs in the 90s (Sept. 1915 had the most - five)

 

Here are recaps from nine previous Septembers:

2022

2021

2020

2019

2018

2017

2016

2015

2014


September 2022 Weather Recap: Largely Uneventful

 

September header

 

September 2022 had close to average temperatures (+0.3 degrees) and rainfall that was just slightly below average (4.10").   Through 9/22 temperatures were two degrees above average, but then the following eight days were four degrees cooler than average.  11 days had mean temperatures that were very close to average (i.e., between one degree below and one degree above average), the most of any month since September 2016.  The month's biggest daily rainfall, 1.11" on 9/25, poured down in a little less than an hour.  (Ironically, 9/25 is one of the least likely dates of the year to report measurable rain.)

 

The spread between the month's coolest (49° on 9/24) and hottest readings (90° on 9/4) was 41 degrees, the widest spread in September since 2015.   Although the hottest and chilliest readings were 20 days apart, the days with the most above average and most below average mean temperatures were just four days apart (9/19, with a high/low of 85°/68° was nine degrees above average; 9/23, with a high/low of 63°/51°, was ten degrees below average).

 

The 90° reading on 9/4 was the 25th reading of 90+ of the year, making 2022 the 20th year with 25 or more (all since 1936).  Of these years, 2022's hot readings were "coolest", with an average of 91.8° (0.1 degree cooler than 1959, which had 27 days in the 90s).

 

Finally, what was likely the last low of 70° this year  occurred on 9/5.  The last time this occurrence was so early was in 2014.  (FYI, a low in the 70s in October has occurred in nine years since 1869.)  In total, 2022 had 50 days with lows of 70+; only eleven other years have had more (the most was 61 in 1906, and 60 in 2005).  

 

Here are are weather recaps from eight previous Septembers:

2021

2020

2019

2018

2017

2016

2015

2014

   


Hurricanes & Tropical Storms That Affected New York Before 1970

 

Hurricane swirling clouds

 

Similar to tropical systems that have lashed NYC since 1970, the average frequency in the years before 1970 is once every two years.  What follows is a year-by-year listing of more than 50 pre-1970 hurricanes (as well as remnants of downgraded storms).  1954 stands out for having four tropical systems that affected the metro area.  At the other end of the spectrum, the 20 years between 1894 and 1914 saw just three tropical systems in total.  Please note that the first named storm to affect New York, Barbara, was in 1953.

 

1869

October 2-3 - Four inches of rain was produced by a hurricane that struck Cape Cod (1.84" fell on the 2nd, 2.16" on the 3rd).

1872

October 26 - The center of circulation from a dissipating hurricane got very close to Manhattan as it moved northeastward, dropping 1.56" of rain.

1874

September 29 – What was once the season's sixth hurricane moved over New York as a tropical storm, dropping 0.64" of rain on Central Park.  This was considerably less than the seven inches of rain that flooded the City from Sept. 16-18 from a non-tropical system.

1876

September 17 - Heavy rain from a minimal hurricane that raced inland through North Carolina and Virginia dumped 3.37" of rain in Central Park (a record for the date that still stands).

1877

October 4 - A dissipating tropical storm dumped 4.05" of rain in Central Park (a record for the date that still stands).

 

Heavy rain clip art2

 

1878

October 23 - The center of a dissipated hurricane and tropical storm, referred to as the "Gale of 1878", moved west of Manhattan.  Shortly after daybreak winds gusted over 50 mph, and 0.73" of rain was measured in Central Park.

1879

August 18 - 3.95" of rain flooded the City from a hurricane that struck North Carolina this morning and raced up the coast during the day.  This amount was a record for the date (a record that still stands).

1880

September 9-10 - Rain from a hurricane moving north from South Carolina started late on the 9th (0.67" of rain fell) and continued into the morning of the 10th (adding 0.54"). 

1882

September 11 - Rain from a tropical storm amounted to 3.23", with much of it (2.57") falling today.

September 23 - Less than two weeks after a tropical storm soaked the City, another tropical system brought more flooding rains to the Mid-Atlantic states, and drenched New York with its greatest rainfall for any calendar date - 8.28".  And in the preceding two days 3.52" of rain fell.  With a total of 16.85" of rain for the entirety of September (most of which fell between the 11th and 23rd), this was NYC's wettest month on record until Aug. 2011 when 18.95" was measured.

 

Heavy rain

1885

October 13 - A tropical storm moved northward through central Pennsylvania and dropped 1.50" of rain in Central Park. 

1886

June 23 - An early tropical storm passing to the south of New York dropped 1.20" of rain.  Cloud cover and rain kept the temperature in the 60s all day (the high/low was 66°/62°).

1888

August 21 - As it traveled just north of the City on its way to New England, the remnants of a category 3 hurricane that struck south Florida and later Louisianar soaked the City with 4.12" of rain (a record for the date that still stands).

1889

September 10-13 - A dissipating hurricane stalled off the Delmarva Peninsula and brought bands of rain over the course of four days, amounting to 4.46", with much of it (3.34") falling on the 12th and 13th.  Except for one hour during the afternoon of the 13th, the temperature was stuck in the 60s.  These four days were the start of a streak of nine days in a row with rain (and ten out of eleven); total rainfall during this period was around six inches.

1893

August 19-20 – A hurricane approached New York during the evening.  A peak gust of 85 mph was clocked and 3.81" of rain fell (1.34" today, and 2.34" on the 20th).

August 23 – Just four days after a hurricane lashed the City, a tropical storm passed to the west and dumped 3.61" of rain.

October 23 - A shield of heavy rain from a tropical storm that passed over the Delmarva Peninsula soaked the City with 2.46".

1903

September 16 - A category 1 hurricane made landfall on the Jersey shore in the morning, delivering a brief period of heavy rain to New York between 11 AM-2 PM; 1.63" was measured.

October 8-9, 1903 - A stalled hurricane (that weakened to tropical storm status), and a low-pressure system that formed along an approaching cold front, combined to create a tremendous rainstorm that produced 11.63" over 26 hours.  The deluge started late in the morning of the 8th (4.30" was measured) and continued thru mid-afternoon on the 9th (when 7.33" fell).  Rain fell at a rate of an inch every two hours for a large portion of the storm; at its most intense, 2.54" fell from 9-11 AM on the 9th.  At the time the rainfall on the storm's second day was New York's second greatest daily amount (behind 8.28” that fell 21 years earlier on Sept. 23); it's now ranked fourth.

1904

September 14-15 - After three weeks in which just 0.01" of rain fell, 3.84" poured down from a hurricane that crossed the eastern end of Long Island,and tore 19 barges from their moorings in New York Harbor.  The rain was split pretty evenly between the evening of 9/14 and the following morning.

1915

August 4 – What was the season’s first hurricane, which developed near Florida, brought 3.25” of rain (mostly between 6-10 AM) as it passed by New York City as a tropical storm.  A gust of 53 mph was clocked at Central Park.  Today’s amount of rain was a record for the date (which still stands).

1916

May 16-17 - The remnants of the year's first (and very early) tropical system produced a record amount of rain for the date (2.66"), with almost all of it falling after 4 PM.  And an additional 0.30" fell in the pre-dawn hours of the 17th. 

1924

August 25-26 - A dissipating hurricane southeast of Long Island, moving in the direction of Cape Cod, brought tropical storm-force winds and 3.03" of rain to New York.  Rain began the evening of the 25th and continued thru late morning on the 26th, with 2.29" measured (1.13" fell between midnight and 2 AM).

1925

December 1-5 – A large, meandering, extra-tropical system brought squalls and gusty winds over the course of five days.  2.76” of rain fell during this period, with the wettest day being 12/3, when 1.63” was measured (but none of the rain was torrential; the greatest two-hour totals were 0.41” from midnight-2 AM, and 0.36” between 8-10 PM.  Winds gusting to 35 mph were common on the 3rd and 4th.

1928

September 19-20 - Remnants of the Great Okeechobee Hurricane (which killed 2,500+ in central Florida on 9/17) dampened the City with 1.70" of rain; 1.29" fell on the 19th (showers fell throughout the day, with 0.58" falling between 10 AM-noon), and 0.41" fell in the wee hours of the 20th (with 0.29" falling between midnight-1 AM).

 

Lake okeechobee hurricane of 1928

 

1929

October 1-2 - The remnants of the season's second hurricane moved through eastern Pennsylvania, producing 2.55" of rain.  2.16" of it fell on 10/2, with most of it falling between 5 AM-3 PM.  This amount was a record for the date (which still stands). 

1930  

September 13-14 - A hurricane off the Outer Banks of North Carolina, pushed rain squalls into the area after 10 PM on the 13th that continued through the wee hours of the 14th.  The 0.75" that fell (0.56" of it on the 14th) comprised half of the rainfall of a dry September (at the time, the tenth driest September; now ranked 21st).  This was the smallest amount of rain from a tropical system since 0.73" fell on Oct. 23, 1878.

1932

September 16 - A weakening tropical storm to the southeast of Long Island brought showers.  And although it was just 0.68”, similar to the hurricane of Sept. 1930, it accounted for more than half of the month’s paltry rainfall (8th driest September; now ranked 15th).   This was the third September in a row with less than two inches of rain (then Sept. 1933 and 1934 would each have more than ten inches).

October 17-18 - Tropical moisture from a tropical storm that dissipated over West Virginia, produced 3.24” of rain, much of which fell between 9 PM on the 17th to daybreak on the 18th (2.58”).  The rain was also accompanied by tropical storm-force winds.  This was the most rain to fall from a tropical system since 3.25" fell on Aug. 4, 1915.

1933

August 23 - The remnants of a hurricane that made landfall on the North Carolina/Virginia border moved north through central PA and upstate NY, dumping 2.23” of rain in Central Park, with much of it falling between 4-10 PM.  (0.14” was added in the wee hours of 8/24).  This came on the heels of a coastal storm on 8/21-22, which produced 3.28” of rain.    

1934

June 19 - 1.91” of rain fell, mostly before 9 AM, as the remnants of a category 2 hurricane that made landfall in Louisiana three days earlier moved just to the southeast of the metro area.  This was a record amount of rain for the date (a record that still stands).

September 8 - The strongest hurricane of the season brought heavy rain to the City when it crossed over the eastern end of Long Island.  There were two periods of heavy rain, the first between 6-10 AM, when 1.23" fell, and then much heavier rain fell from 5-11 PM, when 3.26" poured down.  (An additional 0.37" fell at other times during the day, bringing the day's total rainfall to 4.86".)  During the early evening, winds gusted between 45-50 mph.  This hurricane came four days after remnants of a tropical system brought 0.68” on 9/3-4.

1935

September 6 - The remnants of what was the Great Labor Day hurricane in the Florida Keys (nearly 500 were killed) brought heavy rain this morning, with 1.60” measured between 2-10 AM (most of it fell between 4-8 AM).

1936

September 18 - After receiving just 0.08" of rain in the first two-and-a-half weeks of the month, a weakening hurricane to the southeast dumped nearly four inches, with most of it falling between 2 PM and midnight.  It was also a chilly day, with temperatures falling into the upper 50s during the afternoon. 

1938

September 21 - New York was spared the ravages of the history-making hurricane known as the Long Island Express, which made landfall mid-afternoon, 65 miles to the east.  Still, the City had to contend with near hurricane-force winds and four inches of rain, half of which fell between 1-4 PM.  Besides the wind and rain, it was also chilly, with the temperature dropping slowly all day, from the low-60s to low-50s.  Today's deluge followed two days of steady rain that amounted to 3.45".

 

1938 new england hurricane

 

1939

August 19 - The biggest rainfall of the year was produced by the remnants of the season's second hurricane, which made two landfalls in Florida, on the east coast and along the state's Panhandle.  The 2.31" that was measured fell between noon and midnight.  It fell heaviest after 8 PM, when more than half of the rain fell.  

1944

September 14 - "The Great Atlantic Hurricane" raced up the Mid-Atlantic coast and veered to the east of NYC (making landfall near East Hampton on Long Island), dumping 3.82" of rain between 4-11 PM, and lashing the City with gale force winds that gusted between 40 and 50 mph (and 70-80 mph at LaGuardia Airport).  Today's rainfall came on top of 3.94" that fell yesterday and 1.64" the day before for a three-day total of 9.40".  The New York metro area was the bullseye for the heaviest rainfall.

 

Great atlantic hurricane of 1944
 

October 20-21 - The remnants of the season’s 13th hurricane, that made landfall in North Carolina, produced 1.29” of rain between 7 PM-4 AM.

1950

August 19-20 - The season’s first hurricane brought two periods of heavy rain as it moved from Cape Hatteras to Cape Cod.  The first, from 11 AM-4 PM on the 19th saw 1.43”, with 1.04” of it falling between 1-2 PM.  Then, on the 20th, 1.46” was measured between 7 AM-3 PM, with 0.63” falling in the initial hour.  (However, this storm wouldn’t be as severe as Thanksgiving weekend's nor’easter three months later, which blasted the City with winds that gusted to 70 mph.)

1952

February 3-4 – The earliest tropical system on record brought 0.64” of rain late on 2/3 through the morning of 2/4.

September 1 – Remnants of the season’s first hurricane (which made landfall in South Carolina the day before) moved to the west of NYC and brought 1.17” of rain, with most of it falling between 10A-1PM.  This was a little more than half of the month’s total rainfall.

1953

August 14 - Twelve hours of rain from hurricane Barbara between 10 AM-10 PM measured 0.92”, which was almost half of the month’s total rainfall.

Barbara

1954

June 13 - 0.52” of rain fell between 3-7 AM (most of it between 4-5:00) from a tropical storm out in the Atlantic.  After skies cleared, the mercury rose into the upper 80s.

August 30-31 - Hurricane Carol made landfall on eastern Long Island (as a category 3) and brushed the City with gale force winds and 1.71" of rain, which began last night and continued today through late morning. 

September 11 - Less than two weeks after Hurricane Carol, Hurricane Edna made itself known (as it headed to Cape Cod), dumping 3.30" of rain (nearly twice as much as from Carol), with most of it falling in the twelve hours between midnight and noon.  This was the biggest rainfall of the year.

 

Torrential rain
 

October 15 - Powerful hurricane Hazel (category 4 when it made landfall in North Carolina) moved through Pennsylvania on its way to Ontario, Canada.  It brought minimal rain to the City (0.39” was measured, almost all of which fell between 6-7 PM), but winds gusted to 40 mph in Central Park, and 66 mph at La Guardia. 

1955

August 11-13 - Hurricane Connie flooded New York with 7.11" of rain over the course of 39 hours, with the first band of heavy rain moving through late on 8/11.  Although the most rain fell on the 11th (3.62"), the heaviest sustained period of rain would be on the 12th from 3-9 AM, when 2.50" poured down.  Rain was more of an issue than the wind, which gusted between 35-45 mph, well below hurricane force.  This was New York's biggest rainstorm since the Great Hurricane of Sept. 1944.  And while this ranks as one of Central Park's biggest rain totals, LaGuardia Airport picked up five inches more.

August 18-19 - One week after the flooding rains from hurricane Connie, another tropical system, Diane, affected the region, but compared to Connie, Diane moved relatively quickly.  The first band of heavy rain moved in late on the 18th, and by 9 AM on the 19th the rain was over; less than two inches fell, but significant flooding resulted since the ground was over-saturated from the large amounts of rain from Connie.  Sustained winds got no higher than 30 mph (but winds gusted to 54 mph at LaGuardia Airport).

1956

September 27 - Tropical storm Flossy, which was a few hundred miles to the southeast, brought tropical storm-force winds and a small amount of rain (0.21”) from 9 PM-midnight.

1959

June 2 - Remnants of Tropical Storm Arlene produced 1.09” of rain that fell from noon today until 2AM on the 3rd (0.90” fell from 4-11 PM).

July 10 – Remnants of Hurricane Cindy produced 0.50” of rain between 6 PM on 7/10 and 3AM on the following day.

1960

July 30 – Heavy rain produced by tropical storm Brenda, which moved over NYC, amounted to 3.56” during a 12-hour period between 1 AM and 1 PM.  This was the biggest rainstorm in five years (since Hurricane Connie).  At the time this was the second greatest daily rainfall amount in the month of July (it's now third).

September 12 - Rain and high winds from hurricane Donna, which moved just to the east of Manhattan, lashed the area during the morning through the first half of the afternoon.  2.36" of rain fell (heaviest between 11 AM and 2 PM) and winds gusted between 40-50 mph; at LaGuardia Airport winds gusted to 90 mph, and 3.63" of rain fell.

 

Umbrella blown inside out 

 

1961

September 15 – The downgraded hurricane Debbie moved just to the east of NYC, and produced rain for just a three-hour period between 7-10 AM (and only 0.32” was measured).  

Septmber 20-21 – Moving in during the evening of 9/20, what was once Hurricane Esther brought 1.28” of rain, 1.05” of it on the 21st.  Rain fell hardest between 2-4 AM and 10 AM-noon.  (Before it made landfall in North Carolina a few days earlier, Esther was briefly a category 5 storm.)  Tropical storm-force winds lashed the City at around daybreak.  The rain produced by the storm accounted for 75% of the month’s rain (1.70”).

1962

August 28-29, 1962Hurricane Alma brought rain that fell in three stages: in the pre-dawn hours of the morning of the 28th, when 1.35” fell (0.81” of it in a two-hour period), then lighter amounts after 7 PM through 8AM  on the 29th,  and then a mid-afternoon downpour (0.12”).  In total, 1.95” of rain was measured.


Days With Temperatures Stuck in the 60s

 

Stuck in the 60s

October 2021 was distinguished by having six days with highs and lows that were both in the 60s - the most such days in one month.  On average, two or three of these days occur each year, and they've occurred between May and November (ranging from 5/11 to 11/21).  September is the month most likely to have such days, and the date most likely to have one has been 9/17 (in nine years).  The year with the most of these "stuck" days is 1903, with 13 (five other years have had between seven and eleven).  19 years have had none of these days, the last time being in 2019.

 

Chart - stuck in 60s by month
 

Nearly 80% of these days have had measurable rain, with 18% receiving more than an inch, and 75% a half inch or more.  The greatest rainfall on one of these days was 3.84" on Sept. 1, 1927.  (The last time three inches or more fell on a day stuck in the 60s was on Oct. 27, 2017.)  Despite the high likelihood of rain, only two of the last 15 days with temperatures stuck in the 60s had rain.  

Other observations:

  • Average high/low is 67°/62°, with average rainfall at 0.50". 
  • The most prevalent high/low is 68°/60°.  Nearly 70% of the days had highs of 67°, 68° or 69°, while  nearly 75% of the days had lows of 60°, 61°, or 62.°.
  • The warmest low on one of these days is 67°, which happened twice:  Oct. 1, 1902, and July 20, 1869. The coolest high temperature is 62°, which has occurred four times.
  • One of these days had a one-degree diurnal variation (high/low of 66°/65° on Sept. 17, 1869); 12 others had two-degree variations.

I've also written analyses about days stuck in the 30s and 70s.

 

Chart - years with most days stuck in 60s

 


September 2021 Weather Recap: A Record-Setting 3rd Month in a Row with 10+ Inches of Rain

 

  Lee goldberg wabc

September 2021 will long be remembered for the torrential rain that fell the night of 9/1, submerging streets, highways, subway tunnels and residences.  Nearly 50 deaths in the metro area were attributed to the storm (13 of them were in NYC).  This unprecedented deluge was produced by the remnants of hurricane Ida pushing up against a mass of cool air.  Between 5 PM and 1 AM, a little more than seven inches of rain poured down (with three inches falling between 9-10 PM). 

 

Although heavy rain had been predicted, its intensity in such a brief period of time took residents by surprise.  (And although hurricane Henri, two weeks earlier, produced an inch more of rain than Ida, it fell over the course of 48 hours). 

 

Never before had a month started with so much rain, easily breaking the previous record amount on the first day of a month, 4.98" on Oct. 1, 1913.  The 7.13" measured on 9/1 was the fifth greatest amount to fall on a calendar date.  (Earlier this year, February began with a record amount of snow for the first day of any month, 14.8".)

 

Ida flooding nyc
 

The rest of the month had slightly below average rainfall, but just enough to bring September's total to 10.03".  This was the most rain to fall in September since 2004, and it became the sixth rainiest September on record.  It followed the fourth wettest August (10.32"), and third wettest July (11.09").  Never before had Central Park had three months in a row in which each month had more than ten inches of rain. 

 

More than 90% of the month’s of rain was produced by two storms:  7.23” on 9/1-2 and 2.03” on 9/23-24.  0.77” fell on the other 26 days.

 

Looking at temperatures, Sept. 1 was 1.1 degrees milder than average and was the 26th mildest September (tied with four other years).  However, it ranked 13th for mildest average low, and 55th for warmest high.  12 days in a row (Sept. 12-23) had above average temperatures, a streak of days that was four degrees above average.  The rest of the month was one degree cooler than average.

 

The warmest reading was 85° (on 9/15), the same warmest reading as last September (but it had two days with that high).  Also, both Septembers had seven days with highs in the 80s (the average is eleven).

 

Half of the days in September had highs between 75°-79°, which was double the average number - and the most to be in this narrow temperature range on record (second most is 13 days in Sept. 1999, 1927 and 1908).  Just five days had lows cooler than 60°, eight fewer than average.  Only Sept. 1971, 1930, 1908, and 1881 had fewer days (all had four). 

 

Finally, the month was also characterized by a narrow range in its temperature extremes.  Typically, September's chilliest reading is around 50°, the hottest around 90°, but this September it ranged from 54° (on 9/29) to 85° (on 9/15).  Only two other Septembers have had a range that was smaller.  (The greatest range in temperatures in September was 55 degrees in 1929, ranging from 44° to 99°.) 

 

Chart - narrow range of sept temperatures

 

Here are previous September recaps:

2020

2019

2018

2017

2016

2015

2014

 

 

 


September 2020 Weather Recap: Cool & Dry Conditions Sandwiched Between Mild & Wet

 

September 2020

 

September 2020 was a touch milder than average (+0.8 degree), with close to an average amount of rain (3.94").  The month's story can be told by three eight-day periods: Sept. 3-9 was four degrees above average, Sept. 23-30 was six degrees above average, and the middle of the month (Sept. 15-22) was six degrees chillier than average, and rain-free.  Nearly all of the month's nearly four inches of rain was produced by three storm systems: 0.71" on 9/3, 1.20" on 9/10 and 1.61" on 9/29-30. 

 

The month's near average rainfall belied a 16-day streak with no measurable rain (Sept. 11-26).  This was the longest dry streak since the fall of 2017.  These dry conditions were largely due to a strong high pressure system that anchored itself over the Northeast for about a week.  It prevented moisture from hurricane Sally and tropical storm Beta from moving into the area and brought chilly air into the region, delivering the City's earliest lows in the 40s in seven years (49° on 9/21, 48° on 9/22).

 

Just seven days had highs of 80° or warmer, joining ten other Septembers since 1970 with this few.  The warmest reading was 85°, occurring on 9/3 and again on 9/4 (a typical September's hottest reading is around 90°).  The month's average high of 75.5° was the coolest since 2009.  And although the month's average temperature was a touch above average, it was the coolest September since 2013.

 

Chart - septembers by decades

 

Finally, although highs in the 80s/90s and lows in the 70s occasionally occur in October, if 2020's final reading of 80°+ remains at 9/10, it will be one of the earliest dates on record for this occurrence.  Meanwhile, the 58 lows of 70°+ is the third most after 1906 (61) and 2005 (60). 

Here are previous September recaps:

2019

2018

2017

2016

2015

2014

 


September 2019 - One of 10 Driest Septembers On Record

 

September

 

September 2019 was the first month since October 2013 to have less than an inch of rain and was the eighth driest September on record (0.95" was measured).  Thru 9/20 the month had average temperatures, then the last ten days were eight degrees warmer than average, resulting in the month being 2.4 degrees above average (24th warmest since 1869).  Although it was warmer than average, the month had just one low of 70º+, the fewest in September in ten years (there were none in 2009).  It was also the first September since 2011 not to have any highs of 90° or hotter. 

 

This September added to the record set last year when September 2018 was the fourth in a row with an average temperature of 70.0 degrees or warmer.  September 2019, however, was the "coolest" of the five.  However, a record that was tied last September, the sixth September in a row with a high in the 90s, wasn't broken this year as the hottest temperature this was 89°.  (It occurred on 9/23 - the same date as the month's only low in the 70s).

 

Chart - past five septembers

 

Two-thirds of September's paltry amount of rain fell in the first six days of the month, split mostly between Labor Day (when 0.30" fell mid-day, the most to fall on the holiday in sixteen years) and 9/6, when the most northernmost band of hurricane Dorian dropped 0.27" in less than an hour during mid-afternoon.

 

Chart - 10 Wettest Septembers

Finally, humidity of 15% or lower occurs very infrequently in New York, and when it has happened it's been confined to March and April (in the years since 2000) - until 9/19, when it dropped to 15% for a few hours that afternoon.  The last time the humidity was this low in September was on Sept. 11, 2001, when it bottomed out at 16%.

 

Here are recaps of the five previous Septembers:

2018

2017

2016

2015

2014

 

 Sept 15 - lower manhattan



 

 


September 2018 - A Month With Unusually Mild Nights

 

September 2018

 

September 2018 was 2.7 degrees warmer than average.  Like August, its average low was considerably more above average (+4.4 degrees) than its average high (+1.0).  This resulted in a vast difference in their historical rankings, with the average high ranking 60th warmest while the average low was ensconced among the ten warmest, at #4 (overall, the month was the 21st warmest).  The month's other significant story was its rainfall, which amounted to 6.19" - the most in September in seven years.  Furthermore, this was the sixth month this year with more than five inches of precipitation, joining ten other years with this many or more.  And if that wasn't impressive enough, 2018 became just the second year to have these six months concentrated in the first nine months of the year (1998 was the other year). 

Additional points of interest:  

  • The remnants of two hurricanes brought 1.38" of rain on 9/9-10 (Gordon) and 1.19" on 9/18 (Florence).  However, the month's biggest rainstorm was on 9/25 when 1.95" fell. Nearly half of that day's rain poured down in about an hour early in the afternoon.
  • The first full week of the month (week of 9/3) had four days in a row with highs that ranged from 89° to 93°.  The average high/low of 91/76 during these days was twelve degrees above average.  The first day of this hot spell fell on Labor Day, which had a high in the 90s for just the fourth time since 1980. 
  • This was the fourth September in a row with an average temperature warmer than 70.0 degrees, the longest such streak on record.  What's more, the month set a September record for the most days with lows of 67° or warmer (seventeen; the average number is six).  Despite this surfeit of warm nights, the number of days with highs of 80° or warmer was a bit below average (nine).
  • The month's average diurnal variation (the gap between the average high and low) was the smallest for September in more than 100 years (since 1908).  In 2018 it was 11 degrees, well below the average of 16 degrees (based on the past 100 years).
  • This was the record-tying seventh year in a row in which September experienced highs in the 90s, equaling in length the streak of 1940-1946.
  • Like September, August's average low also ranked fourth (its average high ranked 32nd).
  • Typically September is 2.5 degrees cooler than June, but this year it was one degree warmer.  This is the fifth time it's happened since 1980 (most recently in 2015).

 

 Chart - september warmest lows

Here are recaps of the four previous Septembers:

2017

2016

2015

2014

 


Recap of September 2017 Weather: The Great Rebound

 

Rebound

 

After experiencing the coolest start to the month since 1975 (thru 9/12), a complete turnaround occurred, with temperatures nine degrees above average during a streak of sixteen unseasonably warm days (thru 9/28).  This included a record high of 91° on 9/25, the first 90-degree reading since 8/1, and the latest temperature in the 90s since 1970.  As a result of this rebound the month ended up being 2.5 degrees above average, the fourth year in a row in which September had warmer than average temperatures.  (The final two days of the month reverted back to the cool conditions experienced at the beginning of September, but by then such temperatures were close to average.)  Other highlights:

 

  • With just 2.00" of rain, September was the driest month since August of last year (when 1.97" was measured), and the sixth driest September since 1980.  Much of the rain fell in a 12-hour period on the night of 9/2 into the early morning hours of 9/3 (1.27").  No rain fell in the last 11 days of the month, tying an equally long streak in February as the longest dry spell of the year.  (This dry spell continued into the first week of October.)  The month's last rainfall, 0.22" on 9/19, was produced by Hurricane Jose, which New York was on the western edge of.
  • September's average temperature was 3.5 degrees cooler than August's, the closest September has been to August since 1961 (the average difference is 7.2 degrees). 
  • This was the sixth September in a row to have at least one high in the 90s, the longest such streak since one of seven years from 1940 to 1946 (which would be tied in Sept. 2018).
  • The last day of the month and 9/2 had the month's coolest reading, 54°.  However, while this reading was eleven degrees below average on 9/2, it was just one degree below average on 9/30.
  • Although it fell during the cool first part of September, Labor Day was sunny and pleasant with a seasonable high/low of 80/61.
  • The average high/low of 74/59 in the first twelve days of September was followed by a warm 82/69 from Sept. 13-28.
  • Embedded in the sixteen-day streak of unseasonably warm temperatures were five days in a row (Sept 23-27) with mean temperatures 10 degrees or more above average, the longest such streak in 20 months (October 2017 would have a streak that lasted seven days).  Temperatures were 14 degrees above average during these five days, with an average high/low of 87/69.
  • This was the third September in a row with an average temperature of 70.0 degrees or warmer, making this the longest such streak on record.

 

Sept 2017

 

Here are links to September summaries of the previous three years:

September 2016

September 2015

September 2014

 

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September 2016 Weather Review - Summer Hangs On

 

September song

 

September 2016 was characterized by seasonable temperatures at both the beginning and end of the month and unseasonably warm conditions during the days in between (Sept. 6-23); temperatures during this summery two-and-a-half week period were nearly seven degrees above average.  As a whole the month was 3.8 degrees warmer than average, tying Sept. 1983 and 1884 as the tenth warmest on record (this followed the third hottest August). 

 

Three days had highs in the 90s and seven had mean temperatures that were ten degrees or more above average (one of which was the first day of autumn).  There were just five days with below average temperatures.  The most below average was 9/30, with a high of 59/56 (it was the high that was below average, by 11 degrees) - this was the first day in September with a high in the 50s in fifteen years. 

 

50 Deg Highs in Sept 

OTHER SEPTEMBER HIGHLIGHTS

  • The high on Labor Day was 84°, which was the same as Fourth of July and very close to Memorial Day's high (82°).  This was just the third time since 1970 that that three summer holidays had very similar highs.  But whereas Memorial Day's high was seven degrees above average and Labor Day's five above, 4th of July's was at the seasonal average.
  • On Sept 11 the heat index was 101°.
  • The three 90-degree days in September brought the year's total to 22, five above average and the most since 2010.  The 91-degree reading on 9/14 was the latest high in the 90s since 1995 (when it occurred on 9/15).
  • Although September's rainfall was below average, more fell than in August (2.79" vs. 1.97").  There were no storms that produced an inch or more of rain but three had a half-inch or more (on 9/14, 0.56" poured down in an hour during a late afternoon thunderstorm).  The rainiest day was 9/19 when 0.68" fell.  Since March, all but one month (July, with 7.02") has had below average rainfall, resulting in a deficit of nearly 10 inches in these seven months (20.91" vs. 30.78") .

 

September sun

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