How Hot has 2015 Been?

Keeping cool at Great Falls (MD Side)

Today is the third anniversary of the last time the temperature reached 100 degrees in the Nation’s Capital.  2012 was the third consecutive summer that saw frequent triple-digit heat in Washington, D.C.  However, since then there has been a three year stretch without any 100 degree heat in the Mid-Atlantic Region.

This summer has already featured more 90 degree heat than all of last year combined.  Washington, D.C. averages 36 days of 90 degree heat in a given year and there have already been 27 such days through July 25.  There were only 24 such days last year.  National Weather Service data indicates that Washington, D.C.’s record number of 90 degree days in a year is 67 and occurred twice (in 1980 and 2010).

May 2015 was the warmest on record in the Nation’s Capital and was also drier than average.  That changed markedly in June which was the second wettest on record and also the sixth warmest.  Although 3.37” of rain fell during the first nine days of July, only 0.17” has accumulated at National Airport since then.  Last Sunday, July 19, the high temperature reached 98 degrees in the Nation’s Capital making it the hottest day in more than a year.  

After several days with seasonal temperatures and comfortable relative humidity, significant heat and humidity will return this week.  That’s because the area of high pressure that was responsible for the dry and comfortable weather will shift east of the Nation’s Capital.  That will allow warmer, more humid area to ride southerly winds on the backside of the high pressure system into the Mid-Atlantic Region.  

Although a heat wave last month spanned six days, where temperatures exceeded 90 degrees, this week’s heat wave may exceed that total.   Temperatures could also approach the 100 degree mark by the middle of the week in the Nation’s Capital for the first time in more than three years.