At all three airports, the observed highs were the hottest of the season so far and about 15 to 20 degrees above average. Normal highs are closer to 70 degrees. A high of 88 isn’t “normal” (or average) until the end of June.
Forecasts had called for high temperatures in the upper 80s, with the outside chance of hitting 90. A few non-airport locations in Northern Virginia and Maryland met the 90-degree threshold.
In the District (based on measurements at Reagan National Airport since 1945 and downtown previously), the average first 90-degree day is May 16. Last year, the first 90-degree day didn’t occur until June 3, but July brought the most 90-degree days on record during a calendar month. Washington’s earliest first 90-degree day on record occurred March 22, 1907, whereas its latest first 90 was July 12, 1979.
Wednesday’s record-challenging warmth resulted from southerly winds drawn into the region ahead of a cold front bringing flooding and severe storms from Texas to the Ohio Valley.
Interestingly, the exceptional warmth comes on the date of the District’s latest measurable snowfall on record. On April 28, 1898, a coating of 0.5 inches fell. Measurable snow has never fallen in the area during May, although trace amounts or flurries have been observed.
The Washington region has more warmth to look forward to. Highs on Thursday are forecast to reach the low to mid-80s. We will briefly cool off Friday and Saturday, when highs dip to near 70 before rebounding closer to 80 on Sunday and the beginning of next week.
Correction: Based on a preliminary report, this story initially said BWI Marshall hit 90 degrees, tying the record for the date. But the official high turned out to be 89, so the temperature information has been revised.