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

 

 

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. 

 

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

 

Comments

[William]

this was the first May of all time in which each and every single one of the final six days of the month had measurable rain. however, five other Mays have had a rainier/wetter last six days than this May had experienced.

the total amount of rain from May 26 to May 31 in 1906 was 3.97".
the total amount of rain from May 26 to May 31 in 1940 was 3.63".
the total amount of rain from May 26 to May 31 in 1948 was 3.03".
the total amount of rain from May 26 to May 31 in 1968 was 4.92".
the total amount of rain from May 26 to May 31 in 1984 was 5.54".

[Richard]

Just wanted to let you know I appreciate these and have a look at them every month like clockwork, please keep up the good work.

[Henry]

Hi Rob,
I have seen that you have recently written a post on back door cold fronts with cloudy skies and the winds coming from the northeast. The cool, rainy weather at the end of May was all part of one such massive back door cold front (perhaps one of the longest instances, lasting four days). The unseasonably cool temperatures were the result of northeast winds 10-20 mph, with a peak gust of 36 mph in Central Park.

[Rob]

The cool conditions were more the result of the air flow around the nor'easter-like low pressure system than a cold front. However, a few days earlier (5/26), a cold front from the north that triggered showers in the evening, was more of a back-door event.