Potential Record Heat Looms

Washington, D.C. 7 day forecast (Courtesy: WUSA9)

This is an exciting week in the Nation’s Capital for everyone fascinated by the prospect of triple-digit heat.  There are at least two days in the next seven that have the potential to reach the century mark for the first time in nearly four years.  It’s appropriate that the potentially hottest weather of the summer is occurring during the second half of July.

National Weather Service records illustrate that this is the hottest time of the year across the Mid-Atlantic Region.  Although the longest day of the year is the summer solstice, the hottest time of the year doesn’t occur until almost a month later.  Washington, D.C.’s highest annual average temperature every year is 89 degrees from July 7 through July 22 based on the 30-year average ending in 2010.  Favorable conditions for triple-digit heat in the Nation’s Capital include an area of high pressure with light westerly winds and low to moderate relative humidity.  That’s because drier air heats up and cools off more quickly than moister, more humid air.

A “heat wave” is defined as three or more consecutive days of at least 90 degrees.  While there have been several heat waves during the last few summers with a number of days in the mid to upper 90s, this weekend is setting up as the most extreme heat wave since 2012.  The last 100-degree day in Washington, D.C. was July 26, 2012.  The last time consecutive days of 100-degree heat occurred was on July 17-18, 2012.  Also, the last time there were three or more consecutive days of triple digit heat in Washington, D.C. was from July 5 – 8, 2012.  Since 2012, the hottest temperature in Washington, D.C. was 99 degrees on July 2, 2014.  In addition, the longest heat wave since 2012 was a 13-day stretch last summer from July 24 – August 5 when high temperatures were in the 90s.

The hottest temperature on record in Washington, D.C. is 106 degrees, which occurred twice: on July 20, 1930 and on August 6, 1918.  Those temperatures come with a footnote, though, as they occurred before National Airport opened in 1941 and was made the official weather reporting site for the Nation’s Capital.  The hottest temperature on record at National Airport is 105 degrees, which occurred most recently on July 7, 2012.
 

Record Highs to Beat (in degrees Fahrenheit):

July 22:

Washington, D.C. (National Airport – DCA): 103 (1926)
Dulles Airport, Sterling, Virginia (IAD): 105 (2011 - their overall hottest temperature on record)
Baltimore, Maryland (BWI Airport): 106 (2011)

July 23:

DCA: 102 (2011)
IAD: 99 (2011)
BWI: 102 (2011)

July 24:

DCA: 101 (2010)

IAD: 99 (2010)
BWI: 101 (2010)


July 25:

DCA: 100 (1930)
IAD: 98 (2010)
BWI: 100 (2010)