Comparing July 2019 and July 2018

July 2018 was DC’s fourth wettest on record with 9.73” of rain.  This month will also finish wetter than average with 6.48” of rain at National Airport as of July 26.  In fact, Washingtonians experienced a record rainfall total of 3.44” on July 8, 2019, that nearly equaled DC’s entire July average of 3.73”.

A key difference between July 2018 and July 2019 is how streaky the rain was last year compared to this year.  No measurable July rainfall occurred prior to July 17, 2018.  Then, over the final two weeks of last July, Washingtonians experienced three days with an inch or more of rain.  Those three days alone produced a total of 8.14” or more than 80% of the July 2018 total.  By comparison, this month’s rain has been spread out more evenly with measurable rainfall on 11 of the first 26 days of the month.

In addition to both July 2018 and July 2019 being wetter than average, they both were warmer than average in the Nation’s Capital.  DC’s average July temperature (combining daily high and low temperatures) is 81.9°.  So far this month is 2.1° through July 26.  That’s largely the result of the 12-day heat wave from July 11 – 22.  July 2018 also got off to a dry start and was very hot early on with highs in the 90s on eight of its first 12 days.  However, once the rain began falling on July 17, high temperatures reached the 90s only twice the rest of the month.

DC’s weather this July has been fairly streaky as well, with frequent rainfall over the first week of the month followed by the 12-day heat wave.  While eight of the last 10 July’s have been warmer than average in Washington, D.C., no triple-digit July heat has occurred since 2016.  Official weather measurements for the Nation’s Capital are made at National Airport.  It’s important to make that distinction since both Dulles Airport in Sterling, Virginia and BWI Airport in Baltimore, Maryland both experienced 100° heat earlier this month for the first time since July 25, 2016.

DC’s hottest temperature during 2018 occurred on July 16 when it was 98°.  Similarly, DC’s hottest temperature so far this year of 99° occurred on July 21.  High temperatures reached the 90° plateau yesterday for the 32^nd time this year.  That’s pushed the 2019 total for the Nation’s Capital closer to the annual average of 36 days of 90° heat.  High temperatures reached the 90s on 42 days last year.  While above average that was nowhere near DC’s annual record of 67 days of at least 90° (2010, 1980).