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Hot, Wet New York Summers

Kids.in.rain

 

During the summer months clouds, thunderstorms or winds coming off the ocean often prevent temperatures from rising into the 90s.  However, there are occasional stifling days when high temperatures and thunderstorms co-exist, creating tropical conditions that wouldn't be out of place in Bangkok or Manila.  On average New York experiences about four of these days every year; most occur in July and August.  These downpours are usually of short duration (15 minutes up to a few hours).  This post takes a look at some of these summertime days that featured a combination of wicked heat as well as heavy rainfall. 

 

In the summer of 2019 the most tropical conditions were experienced on July 17.  On that day a severe thunderstorm between 8-9 PM dumped more rain (1.14") than what fell in the previous three weeks.  Earlier in the day sauna-like conditions prevailed as the dew point reached the mid-70s, the temperature rose to 93° and the heat index reached 105°.  It also appeared today would be one of those rare summer days with a low of 80°+, but when tonight's storm moved in the temperature dropped to 73°.  Rain continued after the initial storm, adding an additional 0.68", making this the wettest day of the year.  This moisture was from the remnants of what was hurricane Barry, which had flooded Louisiana earlier in the week. 

 

Three days have had highs of 100° or hotter and thunderstorms:

  • July 18, 2012 - High/Low of 100°/73°. 1.76" of rain fell from  severe thunderstorms that moved through between 2:30 and 5:00; most of the rain fell in the two hours between 2:40 and 4:40.  By 4:00 the temperature had fallen to 73°.  Before the storms moved in the heat index was close to 110° and during the early part of the thunderstorms the dew point was in the mid-70s.
  • July 21, 1991 - High/Low of 102°/74°.  0.46" of rain fell during a thunderstorm between 6-7 PM.  The heat index was between 105° and 110°.
  • July 14, 1954 - High/Low of 100°/69°.  0.37" of rain fell during thunderstorms between 10:30 PM -12:30 AM.  This was also the rainiest day of a dry July.

 

The following six days had hot temperatures and more than two inches of rain (ranked in descending chronological order):

  • Aug. 14, 2005 - High/Low of 96°/72°.  After the high temperature was reached around 2:30 PM three thunderstorms between 3 PM and 1 AM dumped 3.10" of rain.  The storm between 7-8 PM produced 1.70" (with nearly an inch falling in a 20-minute period) while the third storm dumped 0.83" between 10-11 PM.  Dew points were in the low to mid-70s and the heat index rose to 104° in the early afternoon.
  • Aug. 8, 2007 - This hot, wet day was different from the others in that torrential rain fell at dawn.  2.50" poured down between 5-7:00 AM, flooding (and shutting down large portions of the subway system).  And a tornado touched down in Brooklyn.  After a low of 73° the temperature rose to 90° in the afternoon.

 

Torrential rainstorm august 8 2007

 

  • July 21 , 1983 - High/Low of 95°/69°.  The 2.26" of rain that fell in the evening became known as the 'Diana Ross Thunderstorm' because it forced Ross to stop her free concert in Central Park when a severe storm bore down shortly after her performance began.  The rain fell heavily for three hours, from 6:30 until 9:30.
  • Aug. 26 1941 - On a day that had a high/low of 93°/68°, 2.30" of rain fell, most of it between 6:15 and 8 PM.  The day before 1.83" of rain in the early afternoon, but the high was only 75°.
  • July 1, 1933 - After a high of 94°, a heat index in the low 100s and dew points in the low 70s, 2.16" of rain poured down between 8:25 (when the temperature was 88°) and 10:45 PM.
  • June 27, 1932 - High/Low of 90°/72°.  Much of the day's 2.11" of rain fell between 8:00 and 10 PM, but there was also a quick downpour between 5:00 and 6 PM.  During the first half of the afternoon the dew point was in the mid-70s.  

 

And here are other days with highs mostly in the mid-to-upper 90s along with significant rainfall:

  • July 22, 2020 - High/Low of 92°/72° and 1.42" of rain, most of which fell between 6:30 and 7:30 PM during a severe thunderstorm.  The day's low had been 77° but fell into the low 70s during the storm.
  • July 25, 2016 - High/Low of 93°/73° and an inch of rain, which fell from 2:45 until 5:45 PM. During the thunderstorms the dew point rose to 77°
  • July 30, 2015 - A sultry high/low of 87°/76° was accompanied by a series of downpours and thunderstorms that produced 1.95" of rain between 1:00 and 5:00 PM.  During a 20-minute period between 1:24 and 1:44 an inch of rain poured down.  Afternoon dew points were in the oppressive mid-70s and the heat index reached the mid-90s before the rain moved in.J
  • July 7, 2012 - High/Low of 97°/72° and 0.50" of rain.  The rain fell during a late thunderstorm between 10 PM and midnight.
  • July 18, 2006 - High/Low of 95°/71° and 0.69" of rain.  Most of the rain was measured between 10-11 PM.
  • Aug. 2, 2002 - High/Low of 97°/70° and 0.70" of rain.  0.42" poured down in a 15-minute period between 8:15 and 8:30 PM.
  • July 8, 1994 - High/Low of 94°/73° and 0.82" inches of rain.  Much of the rain (0.70") fell from a thunderstorm between 3-4 PM.
  • Aug. 28, 1993 - High/Low of 95°/71° and 0.53" of rain.  All of the rain fell in an hour between 5-6 PM.
  • July 23, 1991 - High/Low of 99°/72° and 0.53" of rain.  A thunderstorm between 5:30 and 7 PM brought all of the rain.
  • July 17, 1988 - High/Low of 94°/71° and 1.21" of rain.  A strong thunderstorm dumped an inch of rain in an hour between 6:30 and 7:30 PM.  Earlier in the day there had also been showers in the wee hours of the morning.
  • July 1, 1971 - High/Low of 94°/73° and 1.56" of rain.  Thunderstorms moved in after 3 PM, with much of the rain falling from two storms between 3-4:00 (0.42") and 6-7:00 (0.65"). 
  • July 18, 1969 - High/Low of 94°/77° and 0.88" of rain.  All of the rain poured down in the hour between 4-5 PM.
  • Aug. 7, 1955 - High/Low of 93°/73° and 0.97" of rain.  The rain fell from a mid-afternoon thunderstorm between 3-4 PM and a nighttime thunderstorm between 9:30-midnight.
  • July 28, 1949 - High/Low of 97°/77° and 1.10" of rain.  (No hourly information is available for this month.)
  • Aug 16, 1944 - High/Low of 96°/73° and 0.88" of rain.  The rain fell between 5:30-8:40 PM.  This was the seventh day in a row with a high of 95° or hotter (and tomorrow would be the eighth).
  • July 11, 1940 - High/Low of 92°/67° and 1.94" of rain. (No hourly information is available for this month.)
  • July 7, 1934 - High/Low of 97°/74° and 0.83" of rain.  Rain fell during two thunderstorms between 8-9 PM and midnight-1 AM.  (The National Weather Service doesn't recognize Daylight Time and uses Standard Time year-round for its official records.)  Before the storms moved in the humidity was around 45% range but then jumped above 90% once the clouds opened up.
  • July 28, 1931 - High/Low of 97°/78° and 0.26" of rain.  The heat index was around 100°, and just before a mid-afternoon thunderstorm moved in it was in the low 100s as the humidity rose from 40% to 80%.  The rain fell in a short period of time, between 4:05 and 4:40 PM.
  • July 13, 1916 - High/Low of 94°/70° and 0.97" of rain.  Two thunderstorms produced the rain, between 4-5 PM and 6-8 PM.  Shortly before the storms moved in the dew point was an incredibly uncomfortable 80° and heat index at 3 PM was a wicked 112°.

 

For an entire summer, the hottest and wettest summer is that of 1991.  It was the 12th hottest and had 15.86" of rain (average amount is 12.50").  Second is the summer of 1983 which was fifth hottest and had 13.48" of rain.  Other warm and wet summers include 2011, 2006 and 1984.

 Heat and Rain

 

Rain forest

 

 

 

 

 

 

 

 

 

 

 

 

 

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Years With No Heat Waves

Heatwave

 

The official definition of a heat wave, established by the National Weather Service, is three or more days in a row with a high of 90° or hotter.  On average, a year has two hot spells like this, and the average heat wave lasts for four days.  The last year without one was in 2014.  Since records began in 1870 there have been 22 years without any, or about once every six or seven years.  (The most in one year was six, in 2010 and 1995).  Some other quick facts:

 

  • The longest gap between years with no heat waves is 28, between 1951 and 1979.  The only back-to-back years with no heat waves was in 1874 and 1875.  And there were one-year gaps in 1996-1998, 1902-1904, 1886-1884 and 1875-1877.
  • 1979 had the most 90-degree days without having a heat wave, 19.  (Average number of days in the 90s per year is 17).   Typically, a year with no heat waves averages seven 90-degree days.  
  • In the years with no heat waves the hottest reading was 97° in 1942.

 

Years With No Heat Waves

 

 


Weather Extremes That Occurred Before Global Warming Became a Concern

November1950noreaster
Runway at LaGuardia Airport flooded during the Great Nor'easter of Nov. 1950

Because we're in the grips of global warming, it seems that every weather anomaly is attributed to the rise in temperatures.  However, unusual weather is a regular part of our climate, with ferocious storms and out-of -the-ordinary heat waves not uncommon in years past.  But it's human nature to forget much of what's come before (or, more likely, to be completely unaware of past conditions).  What follows is a list of more than 50 extreme weather events that New York City experienced in the 20th century.  Today they would cause cries of alarm about global warming, but back in the 1930s, '40s and '50s New Yorkers largely accepted what Mother Nature dished out (and without the benefit of air conditioning!).

 

CRAZY WEATHER OF THE 20TH CENTURY

  • 11.63" of rain fell on Oct. 8-9, 1903.
  • An early June heat wave in 1925 (June 4-6) saw highs of 99°-99°-98° (records that are still standing).
  • Fall 1931 was the warmest on record.  (The six warmest autumns occurred more than 50 years ago.)
  • Winter of 1931-32 was the third warmest ever.  (It was the warmest until the 21st century).  On Jan. 14 the high was 70°.
  • Three of the seven warmest Januarys were in the 1930s (1932, 1933 and 1937)
  • NYC's hottest temperature on record, 106°, occurred on July 9 1936.
  • 1938's Great New England Hurricane/Long Island Express struck in late September.
  • There were 90-degree readings in October 1927, 1938, 1939, and 1941 (and the next occurrence wouldn't be until 2019).
  • The Great Atlantic Hurricane of Sept. 1944 was compared to the '38 New England hurricane; it dumped more than nine inches of rain.
  • Unusually mild March of 1945 and 1946; unusually mild October of 1946 and 1947.
  • The City sweltered through torrid summers in 1944, 1949, 1952, 1953, 1955, 1959, 1961 and 1966.
  • Three days in a row in late August 1948 had highs in the triple-digits.
  • The high reached 72° on Jan. 26, 1950.
  • November 1950 featured highs of 84° and 83° at the beginning of the month, and one of the most intense nor'easters on record, on the the Friday/Saturday after Thanksgiving.
  • The City's earliest 100-degree reading occurred on June 26, 1952.
  • Lengthy late August/early September heat waves broiled the City in 1953 and 1973 (at 12 days, 1953's is still the longest streak of 90-degree days on record).
  • A ferocious nor'easter on Nov. 9, 1953, brought 2.2" of snow, and raked the area with 55-70 mph winds.  Two weeks later there was a four-day streak of 70-degree weather.
  • Flooding rains from tropical storms Connie and Diane occurred in August 1955.
  • The Ash Wednesday nor'easter of March 1962, considered one of the most intense storms of the century, pummeled the Jersey shore and the south shore of Long Island and lasted through five high tides.  Although the City escaped heavy precipitation, gale force winds lashed it for three days, with some gusts as high as 50 mph. 
  • A four-year drought in the mid-1950s was followed by a six-year drought from 1961-1966.
  • Huge rainstorms caused flooding and major disruptions for commuters in Sept. 1966 (5.54"), Sept. 1969 (6.28"), Nov. 1972 (5.60") and Nov. 1977 (9.19").
  • Four days in a row in September 1975 had more than an inch of rain, which amounted to nearly 7.50".
  • A mid-April heat wave in 1976 saw the temperature rise to 96° on Easter Sunday.
  • December 1982 and 1984 were both nearly eight degrees milder than average.
  • 75° on Feb. 24, 1985.
  • December 1989 and January 1990 experienced a wild swing in temperature, with the third coldest December on record (10° below average) followed by the second mildest January (10° above average).
  • A high of 85° was reached on March 13, 1990 - 36 degrees above average.
  • "The Perfect Storm" nor'easter of Halloween 1991 was reminiscent of the Ash Wednesday nor'easter of 1962.
  • An intense nor'easter that struck in December 1992 featured 50-mph winds and a storm surge that flooded the FDR Drive and PATH stations in NJ during AM rush hour.
  • The March 1993 Superstorm/Storm of the Century dumped more than 10 inches of snow; heavy sleet was propelled by 50-60 mph winds.
  • The last four days of March 1998 had an unprecedented streak of highs in the low-to-mid 80s.

Extreme

 

 

 

 

 


Record Highs & Lows: The Home Runs of Weather Reporting

Record.cold Record.heat

 

Because of the excitement they generate I like to think of record high and low temperatures as the home runs of the weather world.  Since weather records for New York go all the way back to 1869 it's a challenge for new ones to be set.  Still, since 2000 (thru 2018) there have been 82 records set or tied, which is about four every year (in 2018 two new record highs were established and two were tied).  However, only nine of the 82 were record lows (most recently on Nov. 11, 2017).  Here are some other interesting facts about New York's temperature extremes:

 

  • The oldest-standing record is the record low of March 1 which goes all the way back to the first year of record keeping, 1869.  The oldest-standing record high occurred nearly as far back, on Jan. 23, 1874.  The newest record (thru the end of 2018) was set on May 3, 2018 when the high reached 92°.
  • 22 record highs and 91 record lows stand alone, i.e. not shared with other years.  The most years tied for a record on one date is six, for record lows on three dates: March 3 (11°), June 2 (48°) and Sept. 8 (54°).  (Ties would be less prevalent if daily temperatures were reported to one decimal point.)
  • There are 21 current records that broke a record set the previous year (12 for lows, nine for highs).  The most recent occurrence was in 1994 when the record high on June 19 broke the previous record set the year before.

 

Ice.surrounds.manhattan

 

  • The most that a record beat the previous record by was 19 degrees on Sept. 7, 1881 (101° vs. 82°).  There are 31 current high temperature records that beat the previous record by 10 degrees or more.  The most recent happened on Feb. 21, 2018 when the new record high was 10 degrees above the previous record (78° vs. 68°).  Eight record lows exceeded the previous record by 10 degrees or more, with the largest difference being 14 degrees on Dec. 18, 1919 (-1° vs. 13°).
  • Of the 150 years since 1869, three had no record highs or lows: 1870, 1958 and 1992.  The year with the most records was 1888 when 49 were set (38 were record lows, 11 record highs).  In recent years the year with the most records was 2001, which had 15 (14 record highs, one record low).  These figures reflect records that may no longer be valid, with many broken in subsequent years.  Looking at records that are still standing, 1888 still has the most, but the figure is 18; it's tied with 1875.  
  • The mildest reading for a record low is 59°, and it has occurred twice - on July 29 (in 1914) and on Aug. 1 (1964).  The lowest temperature for a record high is 54°, which was set on Feb. 7, 1938.  
  • Finally, New York's all time hottest and coldest temperatures occurred just two years apart, in 1934 (-15° on Feb. 9) and in 1936 (106° on July 9).

 

Hotday.newyork.washsquarepark

 

Chart - record highs and lows

 

(This post was inspired by an in-depth compilation of data supplied by Eugene De Marco, another New York City weather hobbyist.)

 

     

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Recap of August 2015: New York's Third Hottest on Record

Hot.august

 

Just three months after an exceptionally warm May, which was New York's second warmest on record, August 2015 crossed the finish line as third warmest.  Although the number of 90-degree days, eight, was double the average, what really contributed to the month being so warm was the absence of any outbreaks of Canadian air masses.  Every day had a high of 80° or warmer - a first for August (a typical August sees seven days with highs cooler than 80°.)  Only four days had below-average mean temperatures; the most below average was just -1.5 degrees on two days.  Below are a number of other noteworthy findings:  

   

  • An extended streak of 80-degree days that began on July 10 continued through August.  By 8/31 it had grown to 53 days, making it the second longest such streak - and it was expected to eclipse 1944's all-time streak of 59 days (it did). 
  • The month was also characterized by plentiful sunshine, with 23 days that were either sunny or clear.  Cloud cover is measured on a scale of 0 to 10, with 0 being clear and 10 overcast.  August averaged a cloud cover rating of 2.1, making it the sunniest month of the past five years (this information is reported sporadically in prior years).  This included sunny/clear sky conditions for the first nine days of the month as well as the final six days.
  • Four years ago August 2011 became the wettest month on record, with 18.95" of rain measured.  Since then the four Augusts that followed have all had less than three inches of rain.  This August measured 2.35", about half the typical amount.  Half of the month's rain poured down during the morning of 8/11.
  • July (2.3 degrees above average) and August (3.8 degrees above average) rank as the fifth warmest July/August combo on record (tied with 1995).  What makes 2015 stand out is that there were a lot less 90-degree days than the other July/August combos ranked in the top 10. 

 

FIVE HOTTEST AUGUSTS
               
  Average   Hottest Days of  
  High Low Mean Temp 90+ 80+ Rain
1980 88.3 72.2 80.3 97 15 28 1.16"
2005 87.1 72.2 79.7 99 9 28 3.96"
2015 86.9 71.0 79.0 95 8 31 2.35"
1988 87.0 70.5 78.8 99 10 26 2.19"
2001 86.5 70.8 78.7 103 8 28 2.56"

 

HOTTEST JULY/AUG COMBOS
         
  Mean Temp Days of
  July Aug July/Aug 90+
1980 79.3 80.3 79.8 26
1955 80.9 78.1 79.5 24
2010 81.3 77.4 79.4 28
1988 79.3 78.8 79.1 23
2015 78.8 79.0 78.9 13
1995 79.2 78.6 78.9 24
1993 80.2 77.2 78.7 30
2005 77.5 79.7 78.6 17
1983 79.5 77.7 78.6 23
1944 79.4 77.8 78.6 28
         

 Sweaty

 

 

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90-Degree Days in September

Hotweather.1940s

 

September is more likely than May to see 90-degree temperatures.  While May experiences a 90-degree day once every three years, September sees one about every two years.  The most such days in occurred in 1961, when there were eight, followed by seven in 1895, 1970 and 1983.  The most consecutive years to have a 90-degree reading in September is eleven, from 1936 to 1946.  (More recently, there was a seven-year streak between 2012-2018.)  The most consecutive years without one is six, from 1885 to 1890.  Finally, three days in September have never had a reading in the 90s: 9/28, 9/29 and 9/30 (9/24 was on this list until 2017). 

 

Only four of New York's ten warmest Septembers are among those with the most days in the 90s: 2015 (warmest September on record/six 90-degree days); 1961 (second warmest September/eight 90-degree days); 1931 (sixth warmest/five 90-degree days); and 1983 (tenth warmest/seven 90-degree days).  And one of the ten years with the most 90-degree days, 1988 (32 days), reported no 90-degree days in September.

 

Lastgaspofsummer

 

Finally, there have been five years with 90-degree readings in October - four were concentrated between 1938-1941, and the last time was in 2019.  Two of those years were back-to-back (1938 and 1939), and in both years there were no 90-degree days in September.  October 1941 had two 90-degree days, including the hottest October reading on record - 94° on 10/6.  In addition, there have been nine  years in which there were 90-degree days in the last ten days of September, most recently in 1980.

 

Most 90 Degree Days in September

 

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The 'Last Gasp' of Summer - Noteworthy Late Summer Warm Spells

Cool.dog

 

Late season heat waves can be great if your vacation happens to coincide with one of them, or if it occurs over the Labor Day weekend.  However, they can also be unwelcome, especially in years when a hot summer doesn't want to let go of its grip (as was the case in 1980, 1983, 1993 and 2010).  Since 1940 there have been more than two dozen of these last gasps of summer (of at least five days).  Some are distinguished by temperature, others by number of days.  For this analysis I discuss seventeen I found to be of greatest interest. (By "late season" I'm referring to any unseasonably warm spell that occurred between Aug. 20 thru about Sept. 20.) 

 

1947 (Aug. 22-26 and Sept. 7-15)

1947 is the only summer in this analysis with two late warm spells.  The first had an average high of 91°, which was nine degrees above average; the second's average high of 86° was ten degrees above average.  

1948 (Aug. 25-30)

This six-day sizzler merits attention because three of the days had highs in the triple digits and two others had highs of 95°.  With an average high/low of 97/76 this is the hottest of the late summer heat waves.

1953 (Aug. 24 - Sept. 5)

This one is the stand-out of all the late season hot spells - all twelve days were in the 90s, including six in a row with highs of 97° or hotter (two of which were in the triple digits).  This is also the longest heat wave in NYC history.

1959 (Aug. 25 - Sept. 9)

This sixteen-day stretch followed an eleven-day hot spell between Aug. 12-22 that ended when two days had unseasonably cool highs in the low 70s.  Then the heat returned beginning 8/25 and continued for sixteen days.  And there would be an early autumn warm streak of nineteen days from Sept. 22 thru Oct. 9.

1961 (Aug. 25 - Sept. 14) & 1964 (Aug. 22 - Sept. 11)

These two are grouped together because they were very similar.  Both lasted for 21 days, the lengthiest of any of the late summer warm spells.  And both had very similar dates.  1961's was a bit hotter than 1964's, with an average high/low of 89/71 versus 87/65; 1961 had nine 90-degree days while 1964 had seven.  However, unlike many of the periods of unseasonably warm weather, there were no highs hotter than 95° in either year.  1964's sultry period was notable because the first three weeks of August had been very cool, five degrees below average, with just one day reporting an above average mean temperature.  

1973 (Aug. 26 - Sept. 5)

Very similar to the late summer heat wave of 1953, this one featured eight days in a row with highs in the 90s, including highs of 98° on 8/28 and again on 8/30.  For the entire eleven-day stretch the average high was 93°.

1979 (Aug. 25 - Sept. 7)

Although three days were in the 90s, what was more striking was the twelve days in a row with lows in the 70s.  The average low during these days was 74°, nine degrees above average. This warm spell was also distinguished by having the smallest difference between the average high and low, twelve degrees.  The only late summer warm spell with a warmer average low would come six years later (but it lasted only five days).  This warm spell featured a cameo by the remnants of hurricane David, which dropped 1.29" of rain on the morning of 9/7.

1980 (Aug. 23 - Sept. 7)

Half of the sixteen days were in the 90s (five of which were 95+) and three other days reached 89°.  The average high for this stretch f days was 90°, ten degrees above average.  (Fifteen days after this hot spell ended the high reached 94° degrees on 9/22.)

1983 (Sept. 3-12)

The highlight was a high of 99° on 9/11, the hottest reading of a hot summer.  And the mercury hit 97° the day before.  Overall, these ten days had an average high of 91°, which was fourteen degrees above average.

2005 (Sept. 12-23)

This was one of the latest of the late incursions of summertime heat; it was also part of 35 days in a row with highs in the 80s that began Aug. 20.  This five-week period was also very dry, with just 0.33" of rain measured in Central Park.

2010 (Aug. 29 - Sept. 2)

The hottest summer on record extended into the first few days of September during this five-day streak of temperatures in the 90s.  And Sept. 3 would probably have reached into the 90s as well if not for cloud cover brought by hurricane Earl (the AM low was a sticky 75°).  Five days after this hot stretch ended saw two days with highs of 89° and 90°.

2014 (Aug. 29 - Sept. 5)

In 2014 New York didn't experience an extended period of hot weather until late in the summer.  Seven of the eight days saw highs of 88° or hotter, with four of them in the low 90s.

2015 (Aug. 30 - Sept 9)

This eleven-day period began with a five-day heat wave and ended with a three-day heat wave, which included the hottest reading of the year, 97°, on Sept. 8. 

2016 (Aug 26-31)

For the third year in a row late summer featured unseasonably warm weather.   Earlier this summer there were two five-day heat waves, and while this six-day period didn't meet the definition of a "heat wave" (i.e., every day has a high of 90+), these days were eight degrees above average.  

 

Summer

 

2018 (Aug. 27 - Sept. 6)

This eleven-day stretch was comprised of two four-day periods of hot weather at the beginning and end, with three close to average days in between.  Each four-day period had three days in the 90s and three days with lows of 75°+.  The average high/low of the entire eleven days was 88/75°, eight degrees above average.  The average low is the warmest of any late summer hot spell of ten days or longer.

 

 Chart - Hottest Late Summer

Chart - Last Gasp of Summer

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Hot Weather Before & After August 1

Before.after

 

In a typical year, about two-thirds of New York's days in the 90s/100s occur before Aug. 1.  Since 1900 there have been 21 years that were significantly "front-loaded", including the recent years of 2011, 2012 and 2013 (see chart below).  And there have been eight years in which no 90-degree temperatures occurred on Aug. 1 or later.  The last time this happened was in 1986.  Meanwhile, the fewest number of days in the 90s before Aug. 1 is one, which occurred in 2004, 1960 and 1902.  And once every seven years the post-Aug. 1 period has had the most 90-degree days (2015 was the most recent of those years).  The two biggest "back-loaded" years were in 1970 when there were seven 90-degree days before Aug. 1 and fifteen in Aug./Sept., and 2015, with six before and fourteen after.

 

August1 

 

The following two charts show the most "front loaded" and most "back loaded" years since 1900, arranged in descending chronological order.

 

Chart - split 90s

 Chart - split90s

 

1991 had the most days in the 90s before Aug. 1, twenty-seven, followed closely by 1993 and 1966, both which had twenty-six.  1980 had the most 90-degree days to occur on Aug. 1 or later, eighteen.  This was four more than the number of 90-degree days before Aug. 1 of that year.  (Both amounts were above average.)

 

Most 90-Deg Days Before Aug. 1
     
   Before August 1
Year August 1 and Later
1991 27 12
1993 26 13
1966 26 9
1999 23 3
1944 23 14
2010 22 15
1949 22 7
1988 22 10
1983 20 16
1953 20 12
1952 20 4
     
     
Most 90-Degree Days After Aug 1
     
  August 1 Before
Year and Later August 1
1980 18 14
2002 16 16
1983 16 20
1959 16 11
2010 15 22
1995 15 14
1970 15 7
2015 14 6
  1944      14  23

 

(Many thanks to Eugene Demarco who's spreadsheet showing year-by-year dates of 90-degree highs made this analysis so much easier to do.)

 

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Early Summer Heat Waves in June

Hotday.newyork.washsquarepark

 

Although the official definition of a heat wave is three or more consecutive days with highs of 90° or hotter, I've relaxed it a bit for this analysis and have included days in the upper 80s, as well as one or two cooler days if they fell between periods of hot weather.  With that established, here are eleven of the more notable hot spells that have occurred in the past 100 years.

 

HOT IN JUNE

2008 (June 7-10) - Although just four days long, the average high was 94.8°, the second hottest of June hot spells. 

2003 (June 24-27) - Besides four readings in the 90s this hot spell also had a low of 79° on June 26, the warmest low in June since 1984 (but it came sixteen days later than 1984's).  Interestingly, even with these four hot days, the month was 2.6 degrees cooler than average (and the coolest in 31 years).  Without these four days the month was four degrees below average. 

1994 (June 14-26) -  At 13 days this is the lengthiest warm spell in June (June 1953 had one of twelve days).  Six days were in the 90s.  The high on June 18 reached 98°; three days earlier, the high was 96°.  The month became the third warmest June on record. 

1984 (June 7-13) - The  hottest period in the summer of 1984 occurred during this seven-day stretch in the second week of June.  The average high/low during this week-long steam bath was 93°/75°, with six of the seven days having highs in the 90s (the rest of the summer had four 90-degree days).  The mean temperature of 83.8 was the second hottest for June hot spells, just 0.1 degree below a four-day heat wave in the middle of June 1956.  But it was the most above average, +14 degrees.  The low on the morning of June 10 was 79°, seventeen degrees above average (and one degree higher than the date's average high).

 

Sweltering.hot

 

1966 (June 20 - July 15) - This hot spell began on June 20 and stretched thru mid-July, but even just the 11 days in June makes it one of the lengthiest for the month.  It's probably best remembered for the 101° high on June 27 (second earliest date for a triple-digit high).  The period in June and July were both seven degrees above average.  And earlier in June there was a six-day period that saw temperatures 10 degrees above average.  Overall, this became the second warmest June on record. 

1957 (June 12-19) - This eight-day long stretch of hot weather duplicated a mid-June heat wave from the previous year, but this one lasted twice as long.  These days were eleven degrees above average, with the last five days all in the 90s (peaking at 95° and 96° on 6/16 and 6/17, respectively). 

1956 (June 13-16) - The mean temperature during this four-day heat wave, 83.9° (13 degrees above average), is the highest of all the periods in this analysis.  On June 14 the high reached 99°. 

1952 (June 15-27) - This stands out because two hot periods, of five days and three days, book-ended three days with highs only in the 60s (averaging 63°).  It's also memorable for having the earliest date for a 100-degree high (June 26) - and the only low in June in the 80s (81°).  There was also a high of 99° on June 25.   

1943 (June 19-28) - Eight of the ten days were in the 90s, including highs of 99° on June 25 and 98° on June 27.  This would become the warmest June on record (a position it still holds).

 

Hotweather.pinterest

 

1925 (June 1-7) - This week-long hot spell during the first week of the month had an average high of 95.0°, twenty-one degrees above average, making it the hottest average high of any of the June heat waves in this analysis.  This included back-to-back highs of 99° on June 4 and 5 (which followed a high of 98° on June 3).  June would be the warmest month of the summer of '25, and at the time it was the warmest June on record (it now ranks sixth). 

1921(June 21-29) - Although the amount wasn't excessive, this is the June hot spell with the most rain.  Six of the nine days had rain, which totaled 1.47" (and 0.78" fell on 6/30).  These nine days saw a four-day heat wave at the onset as well as two days with highs of 88° and two with highs of 89°.  Average high during this sultry period was 89°.

 

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Today in New York Weather History: October 17

 

1938

Today's high was a sizzling 90°, the latest date on record for a 90-degree reading - a record that still stands.  This high was 27 degrees above average.

 

Heatwave

2014

This was the tenth day in the past five weeks to have a high of 71°.  On the first day with this high, 9/14, the reading was four degrees below average, but when the mercury reached 71° today it was eight above average.

 

71deg

2016

After nine days in a row with highs in the seasonable 60s, today's high jumped to 81°, the first 80-degree reading since 9/23, and the first reading in the 80s in October in three years. This was also the 100th day this year to have a high of 80° or warmer, just the seventh year to reach this threshold.  It came a year after the record for the most 80-degree days was set - 114.

2021

Today was the first day since 10/1 to have a below-average mean temperature, as the high/low of 61°/51° was one degree below average.  (The low on 10/1 was also 51°.)

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