D.C.’s Warmest and Wettest Month of the Year

 

NOAA's Temperature Outlook for July 2022

June 2022 finished as a slightly cooler and drier than average month in the Nation’s Capital.  That’s a rare combination given how warm and wet the last 10 – 15 years has been in Washington, D.C. 

July is D.C.’s hottest month of the year based on average high/low temperature kept by NOAA.  Average daily high/low temperatures in Washington, D.C. range from 89°/71° on July 1 to 89°/72° on July 31.  However, 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.  NOAA’s climate averages are based on 30 years of data and are updated every decade.  Last spring NOAA updated its averages to reflect the period of 1991-2020 that replaced the previous data set of 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 for most of July went up from 89° to 90°.  That shouldn’t surprise longtime Washingtonians as six of D.C.’s 10 hottest July’s have occurred just since 2010 based on NOAA data.  Consequently, D.C.’s average July temperature (combining daily high/low temperatures) for the 30-year period of 1981-2010 was 79.8°, but rose to 81.0° when updated to reflect the period of 1991-2020.

D.C.’s hottest July temperature on record is 106° from 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 occurred 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” from the period of 1981-2010.  Two of D.C.’s 10 wettest July’s have occurred at National Airport quite recently in 2017 and 2018.  NOAA’s Climate Prediction Center is expecting July 2022 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.