Historical August Heat

The Beach is a Wonderful Place to Cool Off

Although Washingtonians experienced their first triple-digit heat in four years last month, the current heat wave has been even more extreme with three consecutive days of temperatures at record levels in the Nation’s Capital.  A number of other cities across the eastern United States including Hartford, New York City and Atlantic City also set record highs over the weekend.  Even if temperatures don't reach the century mark for a third consecutive day, the combination of hot temperatures and oppressive humidity will make for heat index temperatures well over 100 degrees for Mid-Atlantic residents today and tomorrow.

Washington, D.C. has had an extreme heat wave with temperatures at or above 95 degrees every day since August 10.  A record high was tied Saturday at National Airport when it reached 99 degrees.  Also, high temperatures reached 101 degrees on Saturday, August 13, tying the daily record and just yesterday the record high of 100 degrees was also tied.  That was the first time since August 16 -17, 1997, that Washingtonians have experienced triple-digit heat on consecutive days in August.

The unusually high heat index temperatures have made the current heat wave especially dangerous.  As I wrote about in Friday’s column, the “heat index” is the feels-like temperature when you factor in relative humidity and air temperature.  Given the very tropical-like dewpoints in the mid-70s for much of the last few days, heat indices of 110 to 120 degrees have been common across the DC Metro Region.  That caused the National Weather Service to issue heat advisories from Virginia to New England, illustrating the danger of the record-setting temperatures.  An excessive heat warning was also issued for Washington, D.C. over the weekend for the first time since 2013. 

Through August 14, Washingtonians have had 10 days at or above 90 degrees this month including 5 days above 95 degrees and 2 days of triple-digit heat.  The Nation’s Capital hasn’t had two days of triple-digit heat in August since 2002 (though not on consecutive days).  Since the hot summer of 1993, Washington, D.C. has averaged approximately 10 days of 90-degree heat and 3 days of 95-degree heat in August with triple digit heat roughly every three years.  We’ve already exceeded August’s average number of 95 and 100 degree days and today will be the eleventh day above 90 degrees.  

Making this summer incredible is the fact that it’s been so hot since July 5.  Despite having only 5 days at or above 90 degrees through Independence Day, Washingtonians still had their sixth warmest July on record with temperatures at or above 90 degrees on 23 of the final 27 days of the month.  In a given year, Washington, D.C. averages 36 days of at least 90 degrees with 38 such days so far this year.