Summer-like Heat and Humidity Return

Residents of the DC Metro Area have enjoyed a nice stretch of warm and dry weather this past weekend with lower relative humidity and high temperatures in the mid-80s.  However, the weather pattern changed with a high of 92° yesterday and a noticeable increase in relative humidity today.  The area of high pressure that brought the comfortable temperatures and low relative humidity to the Nation’s Capital has shifted eastward.

The clockwise flow around the area of high pressure has helped usher more humid weather conditions into the Mid-Atlantic Region due to southerly winds from the Deep South.  That’s helped create favorable conditions for the prospect of showers and thunderstorms the next few days with the approach of a slow moving cold front.  Although extensive cloud cover will prevent widespread temperatures in the 90s today, DC’s already had 44 days in the 90s in 2019.  That’s nine more than the annual average of 36 days of 90° heat.  Last year’s total was only 42 such days.

DC residents could use a little rain as measurable rainfall has only occurred once this month prior to today.  That’s not to say there haven’t been scattered showers and storms in the DC suburbs so far this month, but the only time rainfall was officially observed in DC was last Wednesday, August 7 (0.9”).  Weather measurements for the Nation’s Capital have officially been made at National Airport since the early 1940s.  Despite having measurable rainfall on only one day so far this month, DC has a rainfall surplus of more than five inches this year.  

July 2019 was DC’s third consecutive wetter than average July and finished with nearly double the average amount of monthly rainfall.  Many area residents and tourists alike have enjoyed the relatively dry weather so far this August.  That’s following the month of July that featured rain on 15 days.  Area lawns and gardens are in need of a good watering in many parts of the DC Metro Area due to spotty rainfall the last few weeks.  

August 2019 has gotten off to a much different start than last August.  Washingtonians had measurable rainfall on six of the first seven days of August 2018.  That’s not to say this month won’t end up becoming DC’s third consecutive wetter than average August.  NOAA’s Climate Prediction Center indicates the Mid-Atlantic Region has a 33% chance of above average precipitation over the next 8-14 days.  However, the outlook for the entire month of August is for near average rainfall in the Nation’s Capital.