DC’s hottest and wettest month of the year gets underway

 

NOAA's temperature outlook for July 2023

June 2023 finished as DC’s coolest June since 2009.  With only 2.10” of rain, last month became the third drier than average June over the last four years in the nation’s capital.  Dulles Airport experienced its driest June since 2017 and coolest June since 2003.

July is D.C.’s hottest month of the year based on average high/low temperature kept by NOAA.  The hottest time of the year occurs from July 11 - 27 when D.C.’s average high/low temperatures are 90°/73° from July 11 – July 27.  DC’s average high is 89° the rest of the month.  NOAA’s climate averages are based on 30 years of data and are updated every decade.  NOAA updated its averages in 2021 to reflect the period from 1991-2020 that replaced the previous data set from 1981-2010.

During the previous data set, D.C.’s hottest average daily high temperature was 89° for most of July.  However, since the 2010s were a much warmer decade than the 1980s, D.C.’s average daily high temperature increased from 89° to 90° for most of the month.  That shouldn’t surprise longtime Washingtonians as six of D.C.’s 10 hottest July’s have occurred over just the last 13 years based on NOAA data.  Consequently, D.C.’s average July temperature for the 30-year period from 1981-2010 was 79.8°, but rose to 81.0° when updated to reflect the updated period.

D.C.’s hottest July temperature on record is 106° on July 20, 1930.  That’s tied with a date in August for D.C.’s hottest overall temperature.  More recently, D.C.’s second hottest temperature of 105° occurred on July 7, 2012.  No triple-digit July heat has been recorded in Washington, D.C. since 2016.  D.C.’s coolest July temperature of 52° has occurred several times, most recently on July 4, 1933.

July’s new monthly rainfall average of 4.33” also makes it D.C.’s wettest month of the year.  That represents a significant increase over the old average of 3.73”.  Two of D.C.’s 10 wettest July’s at National Airport occurred quite recently in 2017 and 2018.  NOAA’s Climate Prediction Center is expecting July 2023 to be a warmer and wetter than average month in the D.C. Metro Area.  That would continue the recent trend in the nation’s capital.

Warmest July’s in Washington, D.C. by Average Temperature (Combining Daily High/Lows)

1.  84.5° (2011)
2.  84.0° (2012)
3.  83.9° (2020)
4.  83.1° (2010, 1993)
6.  83.0° (1999)
7.  82.7° (2016)
8.  82.6° (1987)
9.  82.3° (1980)
10.  82.1° (2019, 1955)