A Cool and Wet April

April 2020 is well-positioned to finish as a cooler and wetter than average month.  DC has already exceeded its monthly average of 3.06” with 4.20” of rain through April 23.  There are several more rain chances before the end of the month.  Temperatures have been cooler than average on nine of the last 10 days helping push DC’s average monthly temperature to 0.5° below normal as of yesterday. 

Cooler than average temperatures are expected to continue into early May.  That would ensure April 2020 finishes cooler than average for only the second time in the last decade.  It was only two years ago that Washingtonians last experienced a cooler and wetter than average April.  Although 2018 got off to a drier than average start, DC residents ultimately had the wettest year on record in 2018.  The final nine months of 2018 were exceedingly rainy.

The summer of 2018 was quite hot with June, July and August each having finished warmer than average.  The first half of July 2018 was quite hot and dry with all of three but of the first 16 days warmer than average, with no measurable rainfall.  However, the 9.73” of rain that occurred during the second half of July helped keep temperatures below what they otherwise could have been.  Consequently, August 2018 finished 0.3° warmer than average July 2018.  That’s rather unusual since DC’s average July temperature is 1.7° warmer than August’s.

Prior to 2018, the last time DC residents had both a cooler and wetter than average April was in 2007.  That April was 3.2° cooler than average, with 1.11” more rain than average.  Similar to 2018, August 2007 finished 0.4° warmer than July.  That was the second consecutive year DC residents had a hotter August than July.  DC residents experienced triple-digit heat in August 2007.  Triple-digit heat wouldn’t occur again in the Nation’s Capital until June 2010.

Having a cooler and wetter than average April is a relatively rare occurrence in the Nation’s Capital, with this month poised to become only the third time since 2001.  However, April’s weather is not a reliable predictor of what kind of weather Washingtonians will see during the upcoming summer.  It was just a coincidence that August finished warmer than July did the last two times April was cooler and wetter than average in the Nation’s Capital.  NOAA’s Climate Prediction Center expects May to get off to a cooler than average start in the DC Metro Area, but for the month to ultimately finish warmer than average with near average rainfall.