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August 2021 Weather Recap: Henri Rescues August From "Dullsville"

 

 Hurricane henri aug 2021

 

August was the fourth wettest August on record, but until 8/21 the month had been a dry one, with rainfall 50% below average.  Then, Hurricane Henri produced 8.19" of rain over three days (Aug. 21-23), accounting for nearly 80% of August's 10.32" of rain.  (The other 28 days of the month had just 2.13".)  This was the second month in a row with more than ten inches of rain (July had 11.09", making it the third wettest July),  just the second time this has happened (however, the first time, in March and April 1983, is disputed since the rain gauge in Central Park wasn't functioning properly for much of the year).  Although August's rainfall was less than an inch below that of July, its number of days of measurable precipitation was half as many (nine vs. eighteen).

 

Chart - rainiest back to back months
 

One out of four Augusts have been warmer than July, and August 2021 was one of them (77.5° vs. 76.0°).  The month was 1.4 degrees above average, making it the City's 17th hottest August (out of 153).  However, there was a disparity in rankings of the average high and low, as only five other Augusts have had a warmer average low than this August (2.2 degrees warmer than average), but the average high (just 0.6 above average) was ranked much lower, at #39.  This difference in rankings wasn't unique to this August, as the trend during the 2000s has been for overnight temperatures to be more above average than daytime readings (one of the effects of global warming).

 

After the first five days of the month were five degrees below average, the rest of the month was three above average (with only five of the 26 days having cooler than average mean temperatures).  August had five readings in the 90s, one more than July, and it had five more days than July with lows of 75° or warmer.  August's days in the 90s were comprised of back-to-back days on Aug. 12-13, and a three-day heat wave two days after Henri's departure (Aug. 25-27).  The month's hottest reading was 94° on 8/13.

 

Finally, this was the eighth year in a row in which August had no readings in the 50s.  The coolest temperature was 63° on 8/2.  (Meanwhile, July's streak of 12 years with no lows cooler than 60° was broken this year). 

Henri

Here are monthly recaps for past Augusts:

2020

2019

2018

2017

2016

2015

 

 

 

 

 

 

   


July 2021 - Third Rainiest July Keeps Mid-Summer Heat in Check

 Noahs ark in water

With 11.09" of rain measured in Central Park, July 2021 became the third rainiest July on record (behind 1889 and 1975), and 15th wettest month overall.  This was New York's first month with ten inches or more of precipitation since June 2013 (10.10"), and the most to fall in any month since August 2011, when 18.95" flooded the City (the greatest monthly amount on record). 

 

A little more than half of July's rain fell on three days between July 8-12: 2.27" on 7/8; 2.06" on 7/9, and 1.42" on 7/12.  The amounts of 7/8 and 7/9 set records for the dates.  8.49" of rain fell in the first 12 days of the month (and 9.14" if 6/30 is included), then 2.60" fell thereafter (which was slightly below average for that period). 

 

There were 18 days of measurable rain, which was the second greatest number of days with rain in July.  July 1871 had twenty days, but just half the amount of rain as July 2021.   (Of the 27 months with ten inches or more or precipitation, the average number of days of measurable precipitation is 13.) 

 

Besides being rainy, this was the coolest July since 2009 (and 0.1 degree cooler than July 2014).  When all Julys are considered, July 2021 is in the middle of the pack, temperature-wise, with 54% being warmer.  The combination of a warmer than average June (+2.3 degrees), and July being 1.5 degrees cooler than average, placed these two months closer together (1.7 degrees) than any June/July combo since the summer of 2001 (when July was just 0.3 degree warmer).  Looking at average high and low, July's average high of 83.0 was just 0.5 degree warmer than June's, while the low of 69.0 was 3.0 degrees milder.  Because many days had dew points in the 68°-73° range, the air often felt oppressive rather than cool.

 

So close_colbert
 Chart - july close to june

For the first time since 2009, a reading in the 50s occurred in July - 59° on 7/3.  And on 7/3, the high was only 66°, which was the first high cooler than 70°in July since 2013, and the coolest reading in July since 2005 . The month's coolest and hottest readings were three days apart as a high of 92° occurred on 7/6 (and the 59° reading came three days after June's hottest temperature, 98°, on 6/30).

 

July had four days in the 90s, half as many as June, and the fewest such days in July since 2014, which had three.  (Seven of the Julys between 2000-2009 also had four or fewer days in the 90s.)  Although the number of days of 90+ was half the average for July, the number of lows in the 70s, 16, was an average am0unt (but ten fewer than last year's record amount).

 

July had 8.47" more rain than June's 2.62", but there have been ten other instances where the disparity between two months was even greater (looking only at wet months preceded by dry ones).  The greatest difference occurred in  Sept-Oct 2005, when October had 16.73", which was 16.25" more than September's bone-dry 0.48".

 

Chart - greatest dif in precip btwn 2 mos

Finally, after suffering through sweltering heat, and a nighttime thunderstorm on the last day of June, the last day of July couldn't have been more different, as skies were clear and temperatures on the cool side (high/low of 77°/60°).  While 6/30's high of 98° (14 degrees above average) was the hottest reading on that date since 1964, 7/31's low of 60° (ten degrees below average) was the chilliest since 1956.

 

July 2021
 

Here are other July recaps:

July 2020

July 2019

July 2018

July 2017

July 2016

July 2015

July 2014

 

 

 

 

 


June Weather Recap: Two 4-Day Heat Waves Make June 2021 One of NYC's 10 Hottest

 City sunflower 2021

With a scorching high of 98° on the last day of the month (along with a heat index of 106°), June 2021 became New York's ninth hottest June.  This was Central Park's hottest temperature since 2013, and the hottest reading in June since another 98° high in June 1994.  6/30 was also the last day of the month's second four-day heat wave, which was just the second time there were two heat waves of this length (or longer) in June (the other was in June 1943, the hottest June on record). 

 

The month's eight days with 90+ highs were the most in June since June 1991 (which had nine).  Only four Junes have had more hot days: 1943 (11), 1966 (10), 1925 (9) and 1991 (which was slightly cooler than June 2021, ranking as 14th warmest).

 

The month had nine days with lows in the 70s, tying it for ninth most in June.  The month's five days with lows of 75° or warmer was the most since there were six in June 1943.  (June 1909 had the same number as this June.)  Finally, in the years since 1940, the low of 76° on 6/6 was the fifth earliest date for a low this warm.

 

Ironically, despite the month's warmth, this June had the latest occurrence of a reading in the mid-50s since 1995, occurring on 6/23 (54°).  This was the coolest reading of the month (twelve degrees below average).

 

The month's two four-day heat waves were three weeks apart - June 6-9, and June 27-30.  The first heat wave averaged a high/low of 91°/74° (13 degrees above average), the second was 94°/75° (nine above average).  Both heat waves had a day with significant rainfall at night, 0.47" on 6/8, and 0.65" on 6/30.  Without these heat waves, the other days of the month were one degree cooler than average.

 

Besides the high of 98°, the last day of June was also the rainiest day of the month (0.65").  If it hadn't been for this rainfall, this would have been the second June in a row with less than two inches of rain, something that hadn't happened since 1978 and 1979.  These nighttime thundershowers cooled the temperature to 73°, erasing the day's morning low of 80°.  (If that sultry low had remained the day's low, this would have been the seventh, rather than ninth, hottest June.) 

 

With eight days of 90+ readings by 6/30, 2021 joined 20 other years (since 1869) to have this many by that date (1991 had the most - 15).  The last time there was this many by this date was in 1994.  Prior to that, between 1923-1994, this many days in the 90s by the end of June occurred much more regularly, once every four years.

 

Finally, in an interesting contrast, while the last four days of June had highs in the 90s (eleven degrees above average), the last four days of May all had lows in the 40s (ten degrees below average).

 

Girl_cooling_off_in_fountain_ethiogrio

Here are previous June recaps:

2020

2019

2018

2017

2016


May 2021 Weather Recap: Close to Average Temperature & Rainfall Despite Very Chilly & Wet End

 Wet and chilly memorial day weekend

Last May, the month's weather highlight was an Arctic outbreak in the second week of the month that produced the coldest reading in May (34°) since 1891.  May 2021, meanwhile, experienced one of the chilliest ends of any May, as May 28-31 tied May 1884 for the latest four-day streak with lows in the 40s.  This chilly ending was responsible for the coolest three-day Memorial Day weekend on record. 

 

Chart - 3 chilliest memorial day weekends

Despite the month's chilly ending, an extended period of above-average temperatures from May 15-27,  that was six degrees milder than average, kept the month close to average, temperature-wise.  And a very wet May 28-30, in which 2.57" was measured, balanced what, up until then, had been a dry May (these three wet days had as much rain as the previous six weeks).  So, when all was said and done, the month was very close to average on both the temperature and rainfall fronts (-0.3 degrees, and +0.40").

 

Before May's chilly and rainy close, six days in the 10-day period between May 18-27 had highs in the 80s.  This included highs of 89° and 88° during the weekend of 5/22 and 5/23; by contrast, the following weekend had highs of 51° on both days.  This reading (which was eight degrees colder than the average low for these two dates) tied a record for the coolest high on 5/29, and set a new record (by four degrees) on 5/30.

 

Besides the last four days of the month, which were 13 degrees cooler than average, there was an eight-day period from May 5-12 that was five degrees below average.  (However, the chilliest reading of the month, 42°, was on 5/1.)

 

Finally, the last six days of the month all had measurable precipitation, the longest rainy streak since one of eight days in May 2019 (5/10-17).  However, this year's streak had a touch more rainfall (2.68" vs. 2.56").

 

Here are recaps of the previous six Mays:

2020

2019

2018

2017

2016

2015

 

May 2001


March 2021 Weather Recap: Mild & Rainy Last Two Weeks

 Daffodils of march

 

The first week-and-a-half of March 2021 was exceedingly dry, with just 0.16" falling thru St. Patrick's Day.  (3/1 was the only day with rain.)  Then, in the last two weeks of the month, regular rainfalls returned, with 3.25" measured (more than 50% above average for that period).  The beginning of the month was also on the cold side, with temperatures four degrees colder than average through the 8th (the coldest day was 3/2, with a high/low of 33°/21°).   The rest of the month was six degrees above average, largely due to the last twelve days of the month, which were nine degrees milder than average (high/low of 64°/45°).  Overall, the month was 3.3 degrees above average, and was the 13th mildest March on record (March 2020 was eighth mildest).   The average high was 4.4 degrees above average; the average low was 2.3 above average.

 

The month's highlight was the record high of 82° on 3/26 – the first reading in the 80s in March since 1998 (and the eighth year in which the first 80+ occurred in March).  Besides this first reading in the 80s, March also had the year’s first readings in the 60s (3/9), and 70s (3/11).  This was just the third year in which all three occurrences happened in March, joining 1945 and 1977.

 

82 degrees

 

For the second year in a row, there was no measurable snow in March, just the second time this has happened; the first time was in 1945 and 1946.  And for just the fifth time, February, which was one of the snowiest, was bookended by a January and March with little snowfall.

 

Chart - snowy february bookended by snow-free months

There were eight days that were ten or more degrees milder than average (including 3/26's high of 82°, which was 29 degrees above average), and two others that were more than ten degrees colder than average.  14 days were five degrees or more above average (including eight in a row, from 3/21-3/28, that were seven or more degrees above average); eight were five degrees or more below average.

 

After back-to-back months with diurnal variations below ten degrees, March's was 16.6 degrees (average is 15.1).  Additionally, the range between the coldest and highest temperatures in March was 61 degrees (21° and 82°), the widest range since 2007, when it was 67 degrees (11° and 78°).  This was in contrast to January and February, both which had variations of only 37 degrees. (The greatest range in March is 72 degrees, which was in 1990, when the temperature extremes were 13° and 85°.) 

 

The month had fifteen days with humidity levels that dropped to 25% or lower at some point in the day (usually in the afternoon), with the lowest being 12% on 3/15 at 4:00 PM (and there were two other days with lowest humidity at 13%).  Finally, ten days had a peak wind gust of 35 mph or higher, with the peak gust at 44 mph, which was clocked during the evening of the 26th (the day with a high of 82°).   

 

Here are March recaps from the five previous years:

2020

2019

2018

2017

2016

 

 March_2021_iphone_calendar-scaled

 

 


February 2021 Recap: New York Trudges Through One of Snowiest Februarys On Record

 

Feb 1 snowstorm nbc nightly news

 

February 2021 was 1.1 degrees colder than average, and the eighth snowiest February on record, with 26.0” measured.  More than half of the snow fell on Feb. 1, when 14.8” piled up (in total, the storm produced 17.4”).  This was the largest accumulation ever reported on the first day of February.  Another highlight of the month was the severe Arctic outbreak in the middle of the month that plunged Texas, the southern Plains, Midwest and Ohio Valley into the deep-freeze, but barely brushed New York.  Although the month was colder than average, the coldest reading was just 17° (the month's only reading in the teens).  The month's colder than average status was driven by the average high, which was 2.7 degrees colder than average; meanwhile, the average low was slightly above average (+0.5 degree).  Finally, with 5.13" of precipitation, the month was among the ten wettest Februarys since 1930 (and 21st wettest going back to 1869).

 

This was New York's coldest February since 2015 and the first colder-than-average month since May 2020. It was also the first year since 2015 in which neither January or February had any readings of 60° or milder.  The 15-day period between Feb. 7 and 21 was five degrees colder than average (high/low of 35°/25°), with all but one of the days colder than average (10.2" of snow fell during this period).  Temperatures rebounded during the last six days of the month, and were six degrees milder than average (high/low of 48°/38°); temperatures were above freezing for the entire period.

 

Like January, there was just a 37-degree range between February's coldest and mildest readings (17° and 54° in February, 14° and 51° in January).  Since 1950, the typical range has been 49 degrees (11° and 60°); during these year just six other Februarys have had a smaller range, most recently in 2010 (29 degrees).  Meanwhile, the month's average diurnal variation (the difference between the high and low temperature) was just 9.5 degrees (February's average is 13.5 degrees), making it just the fourth February with a diurnal variation less than 10 degrees.  (The others were in 2010, 1969 and 1869.)  This was only the second Jan./Feb. in which both months had diurnal variations less than ten degrees.  (The other time it happened was in 1869.)  Jan./Feb. 2021’s diurnal variation of 9.7 degrees beat out 1869's by 0.1 degree for smallest variation.

 

Chart - smallest diurnal variation jan_feb

 

This winter’s December-February combo was the ninth snowiest on record.  It joined four other pairs from this century (the other five happened before the winter of 1962).

 

Chart - snowiest dec_feb combinatons

 

February 2021 joined sixteen other Februarys that had 20 inches or more of snow.  It was milder than all but two of them (February 1983 and 2006).

 

Chart - mildest februarys with 20 inches of snow

 

Looking at December thru March, February 2021 ranks as the fifteenth snowiest month, just 0.1" behind Feb. 2003, Jan. 1996 and Feb. 1894.  This February's hefty snow accumulation was quite a contrast to last February, which saw just a trace.

 

Chart - snowy feb preceded by no snow feb

Here are other February recaps:

2020

2019

2018

2017

2015

 

 


January 2021 Weather Recap - Winter Makes Late Appearance

Late bloomer

 

If you're not a "winter person", then the first three weeks of January 2021 were tolerable, as temperatures were six degrees above average (with every day but two above average), and there was no snow (average high/low was 43°/33°).  Then, the jet stream shifted, and the last nine days of the month were five degrees colder than average (high/low of 33°/22°).  On the last day of the month conditions became even more wintry.  Up until the 31st, it appeared the month was going to be among the five least snowy Januarys on record, as just 0.1" had fallen.  But then, the opening volley of snow from a snowstorm that would bury the City on Feb. 1 dropped two inches between 6:00 and midnight - the most snow to fall on this date since 1898. 

 

Despite being 2.2 degrees above average, January's mildest reading was just 51° (on Jan. 2).  This was, by far, the mildest January to have its warmest reading this cool.  Previous Januarys with mildest readings that were either 50°, 51°, or 52°, had an average monthly temperature of 28.9°, which is is 5.9 degrees colder than January 2021 (34.8°). 

 

The coldest day of the month was the 29th, with a high/low of 25°/14° (thirteen degrees colder than average).  This was the coldest day in two years (since a high/low of 21°/11° on Feb. 1, 2019).  

 

With just 2.1" measured, this was the third consecutive January with snowfall that was well below average (January 2019, had 1.1", January 2020 had 2.3").  It was the fifth string of low-snow Januarys.

 

Chart - minimal snow consecutive januarys

 

With an average high of 39.7°, and an average low of 29.8°, January's diurnal variation was just 9.9 degrees, making this just the third January whose average high and low was less than ten degrees apart.  The two others were in 2017 and 1869 (variations of 9.4 and 9.8 degrees, respectively).  This narrow diurnal variation was largely due to the month's average low being notably more above average than the average high (+2.9 degrees vs. +1.4 degrees, respectively).

 

Here are previous January recaps:

2020

2019

2018

2017

2016

2015

2014

 

 

 


December 2020 Weather Recap: Two Storms Grab Headlines

Janice huff wnbc dec2020

 

The lasting memory of December 2020 will no doubt be the snowstorm of Dec. 16-17.  The 10.5" of snow that piled up was the biggest snowfall in December since 2010 and the thirteenth December snowfall of 10"+.  Another highlight was the intense rainstorm that blew through the City on Christmas morning.  The month was 1.7 degrees above average - the City's 34th mildest December (since 1869).  But despite being milder than average it had more days with highs of 32° or colder than all of last winter (four vs. three).  Additionally, the big snowstorm produced more than twice as much snow as the previous winter (10.5" vs. 4.8").

 

  • Five days had highs of 55° or milder while six days had lows of 25° or colder.  There were three days with highs in the low 60s, evenly spaced, on 12/1 (62°), 12/13 (62°) and 12/25 (61°).  Five of the six days with lows of 25° or colder had lows of 24° (the outlier was the reading of 20° on 12/19).
  • The mildest and coldest periods of December occurred during the fifteen-day period from Dec. 11 thru Dec. 25.

 

Chart - december 2020 coldest_mildest periods

 

  • Christmas Day's high of 61° (before sunrise) made it the eighth Christmas with a high in the 60s, and the 0.92" of rain that fell was the third greatest amount on the holiday.  After the high was reached the temperature fell steadily throughout the day and was down to 29° by midnight.  This 32-degree drop was the greatest of any calendar date in 2020.
  • Although the month was on the mild side, five Decembers in the past ten years were even milder.

 

Chart - mildest decembers since 2011

 

  • December 2020 was the 29th December with ten or more inches of snow (nearly 20% of all Decembers).  However, it was the second mildest December (after Dec. 1912) to have this much snow.  Although their average temperatures weren't quite as mild as this December, the Decembers of 1948, 1959 and 2003 had considerably more snow (25.3", 15.8" and 19.8", respectively).

 

Chart - snowy mild decembers

 

  • Much of the month's 4.61" of precipitation (0.61" above average) fell from three storm systems, all which produced more than an inch of precipitation:  1.13" on Dec. 4-5; 1.52" on Dec. 16-17; and 1.16" on Dec. 24-25.
  • Finally, similar to November, December had a lot of days with gusty winds, with Central Park having nine days with a peak gust of 33 mph or more.  The peak gust of 47 mph occurred early Christmas morning.

 

Chart - December peak wind gusts

 Snowstorm of dec 1617 2020

 

Other December recaps:

2019

2018

2017

2016

2015

 

 

 


November 2020 Reigns As Mildest November On Record

WashSqPk_Nov2020

 

November 2020 was 5.2 degrees warmer than average and became the warmest November on record, supplanting November 2015 by 0.2 degrees.  Sixteen days had highs in the 60s or 70s (one fewer than the 1931 record).  What stood out was a streak of six days with highs in the 70s from Nov. 6-11, the longest such streak to occur in November.  (And the seven days between Nov. 4-10 all had clear or mostly sunny skies.) Conditions on Thanksgiving Day were noteworthy as well.  Although the high of 65° wasn't the warmest on record (it tied for third warmest), its low of 55° was.  (Just two years ago Thanksgiving Day had a high/low of 28°/17°.)  It was also one the seventh rainiest Thanksgiving, with 0.79" falling in the morning.  What follows are a few other observations:

 

  • Typically, November is 5.4 degrees cooler than April.  This year, however, it was 2.4 degrees milder and became just the tenth November to be milder than April.  (Nov. 1975 was warmer than April by the greatest margin, +4.4 degrees.)
  • The eight-day period between Nov. 5-12 was 14 degrees above average.  The rest of the month was two degrees above average.  These 22 days included four days that were ten or more degrees above average and two other days that were ten or more below average.  Overall the month had nineteen days that were five or more degrees above average.
  • At 3.99", the month's rainfall was an average amount, and that was thanks to a rainstorm that brought 0.98" on the last day of the month.  It was also the month's biggest rainstorm.  This storm was accompanied by gusty winds.  The peak gust was 35 mph, which was the seventh day of the month to report a peak gust of 30 mph or greater (the area's three major airports, LGA, JFK and EWR had gusts of 30 mph+ on ten, twelve and nine days, respectively, and their peak gusts were much higher).

 

Chart - wind gusts nov 2020 

  • The three warmest Novembers have all occurred in the 21st century, as well as half of the ten warmest and half of the top 12.
  • Despite being the warmest November on record, this November is tied with Nov. 2011 for warmest average high and tied for fourth mildest average low.  Additionally, Nov. 2020 had two days with sub-freezing low temperatures (both were 30°) while half of the ten mildest Novembers had coldest readings that were above freezing.
  • Besides this November, Nov. 1994 and Nov. 1975 also had six days in the 70s (but they weren't consecutive).  But they rank second behind Nov. 1953, which had seven such days.

 
 Chart - 10 mildest novembers2

Here are five previous November recaps:

2019

2018

2017

2016

2015

 

 Nov 7 high rises on hudson

 

 


October 2020 Weather Recap: 'Mother Nature' Dresses Up as 'Jack Frost' for Halloween

New york in fall 2020

 

October 2020 was slightly milder and wetter than average in New York.  The month's first week-and-a-half was uneventful, with just 0.06" of rain.  Then three significant rain events soaked the City, each bringing more than an inch of rain: 1.30" fell on 10/12-13; 1.36" on 10/17 and 2.17" on 10/29-30.  The first and third rainmakers were from remnants of hurricanes Delta and Zeta.  The month ended up with 5.05" of rain, 0.65" above average.  Overall, the month was one degree above average, making it the 11th October in a row that was milder than average.  The low was nearly two degrees above average while the high was just about average (+0.1 degree). 

 

Until the end of the month the chilliest reading had been 44°, which would have been one of the mildest readings for this distinction in October (October 1946's and 1971's coolest reading was 45°; October 2007's was 44°; last October's was 43°).  But then a shot of Arctic air followed the rainstorm of 10/29-30 and Halloween morning dawned with a low of 32°, the coldest reading in October since 1988.  This was three weeks earlier than the average date of the first freezing or colder reading in Central Park.

 

Jack_frost

 

The month's mildest reading was 74° (on 10/7), which was the coolest warmest reading in October since 2009, which also had a mildest reading of 74° (October 2009 was the last time the month was chillier than average).  The last time the warmest reading was cooler than this was in 1987, when it was 72°.  (By contrast, last October's warmest reading was a sizzling 93°.)  There were just six days with highs in the 70s (the October average is nine), none of which occurred back-to-back.  This was just the third time this has happened in October in the past 100 years.  And this October was the only one of the three that was above average temperature-wise.

 

Chart - back to back 70s in Oct

Although the month was one degree milder than average, both the warmest and chilliest readings of October were six degrees cooler than what the average warmest and chilliest readings are in October.

 

Finally, there were just eight days with mean temperatures five degrees or more above average, and four days that were five degrees or more below average.  The lengthiest streak of days that were five degrees or more above average was five (10/20-24); this streak was nine degrees above average (high/low of 69°/58°).  There were no extended periods of significantly chillier than average temperatures, but the last two days of the month were twelve degrees below average (high/low of 47°/34°).

 

Geese on the pier

 

Here are previous recaps of October's weather:

2019

2018

2017

2016