D.C.’s Wet Start to July

 

The first half of July has been cooler and wetter than average.  The warmest temperature so far this month was 94° on July 6.  However, only five days saw highs in the 90s.  Consequently, D.C.’s average monthly temperature (combining daily high/low temperatures) over the first half of July 2022 was 1.2° below average. 

One of the key reasons it’s been much cooler than average during the last two weeks is the frequency of clouds and rain.  Rain occurred at National Airport on 10 of the first 16 days of the month.  The wettest day was July 9 with 4.05” of rain for D.C.’s wettest July day since 1970.  Another 1.38” occurred on July 16 and that set a new daily rainfall record at National Airport.  A total of 6.56” of rain has occurred since July 1 which is significantly above D.C.’s monthly average of 4.33”.  Moreover, another two weeks of July remain when that total can only increase.

Having a wetter than average July is not unusual in the Nation’s Capital as seven of the last 10 have been wetter than average.  To add to that, two of the last five July’s have ranked among D.C.’s five wettest on record.  However, a wetter than average month doesn’t always equate to a cooler than average month.  A good example of this occurred in July 2018, which finished both warmer and significantly wetter than average.

No rain occurred in Washington, D.C. from July 1 – July 16, 2018 for D.C.’s driest start to July since 1963.  During the same period in 2018, Washingtonians had 10 days with highs in the 90s.  However, the period of July 17 – July 31 in 2018 was exceptionally rainy, which resulted in a monthly rainfall total of 9.73”, which ranks as D.C.’s fourth wettest.  Because the first half of the month was so warm, July 2018 finished both warmer and wetter than average.

In sum, the first half of July 2022 has been cooler and wetter than average.  But NOAA’s Climate Prediction Center expects warmer than average weather over the next two weeks in the D.C. Metro Area.  A prolonged heat wave with a number of days in the 90s will get underway this week.  That should offset the cool start to this month and help July 2022 finish as a warmer than average month.