D.C. To Have First 90 Degree Day This Weekend

By Chris Martz | May 16, 2019

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While April 2019 sure had it's fair share of 80 degree days in our nation's capitol, not to mention ranking among the warmest on record, the mercury did not climb to 90°F once during the course of the month. The highest temperature achieved last month was 84°F which was recorded at DCA on April 8th. To the contrary, the low temperature last month was 34°F on April Fools Day (April 1st).

So far in the month of May, Washington, D.C. has recorded three nonconsecutive 80° days; 87°F on the 2nd, 81°F on the 7th, and 82°F on the 10th. 

As a ridge of high pressure builds in over the eastern half of the U.S. late week, we are expecting temperatures to soar into the mid to upper 80s and low 90s, before some real heat builds in this weekend. 

Map via Tropical Tidbits.

On my 7-day forecast, Sunday is forecast to be our first 90° day in D.C. Whether we actually reach 90°F or not come Sunday afternoon is unknown, but some models are very aggressive with the maximum temperature that afternoon.

A month or so ago, I decided to do a little research, and I plotted a graph of the first 80°, 90°, and 100° days of the year by day number in Washington, D.C. As you can see by the graph below, the earliest 90°+ days have come earlier by about nine days - and you could argue that's due to various different reasons. The 30-year average (1981-2010) date for the first 90° day is May 17th; the 1881-1910 average was May 26th.

For a bonus, the earliest 90° day in D.C. occurred on March 22, 1907 and the latest first 90° day occurred on July 12, 1979.

All historical climate data presented in this blog can be accessed from xmACIS2.