An Unofficial End to Summer ?

Meteorologists consider the end of August the unofficial end of summer since “meteorological summer” is defined as the three-month period of June, July and August.  By coincidence, August 31 coincides with the Labor Day weekend this year, another benchmark people cite as an unofficial end to summer.  August 2019 will finish as a warmer and drier than average month in the Nation’s Capital.

A total of only 1.99” of rain occurred this month in Washington, DC.  That’s well below the monthly average of 2.93”.  August 2019 will finish as DC’s driest month, overall, since March 2018 (1.92”).  DC’s wettest day this month occurred on August 7 with 0.9”.  By comparison, August 2018 was significantly wetter than average.  DC had two days last August with more than an inch of rain.

This month’s was dominated by a semi-permanent weather feature common this time of year known as the “Bermuda High.”  That’s a sprawling area of high pressure that tends to suppress cloud development and rainfall.  Unlike past Augusts, no tropical systems impacted the Mid-Atlantic this year.  For example, the remnants of Hurricane Irene brought a prolific amount of rainfall to the DC Metro Area in 2011.

Twenty of the first 22 days of August were warmer than average in the Nation’s Capital – with 15 days of 90° heat.  That’s 50% more than DC’s August average of 10 days of 90° heat.  DC’s hottest temperature this month was 98° on August 19, while the coolest temperature of 64° occurred twice (August 24, 26).  Temperatures have actually felt more like fall in the Nation’s Capital since August 23.  Today was actually the first day of 90° heat since August 22 and there have even been two days with highs in the 70s over the last eight days.

Late August can be quite hot in the Nation’s Capital.  For example, 90° heat occurred on nine of the final 10 days of August 1998.  Five consecutive days of 90° heat also occurred from August 27 – 31, 2018.  Those stretches featured predominantly hot and dry weather.  On the other hand, August 2017 was a cooler than average month in the Nation’s Capital and had a chilly and wet conclusion.  NOAA’s outlook for September is for an equal chance of above or below average temperatures in the Mid-Atlantic Region with the potential for above average rainfall.