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August 2021

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