We predict a muggy May in D.C. area with warm weather, plenty of rain

May has kicked off feeling more like June, and it may well seem like the weather has fast-forwarded ahead for most of the upcoming month.

Our outlook for May projects that temperatures will be about 2 to 5 degrees higher than normal, with an average temperature between 69 and 72 degrees (the record-warmest May average is 73.2 degrees, from 2015).

We’re calling for about 4 to 4.5 inches of rain, slightly above the norm of 3.92 inches. The National Weather Service projects we should pick up about a quarter of that in the first week.

While you may be thinking, “If it’s this hot now, just wait until this summer,” May is historically a poor predictor of the season ahead. We’ve experienced very warm May weather ahead of both cool and hot summers. Nonetheless, our warmer-than-normal spring weather to date is forecast to persist in the coming weeks.

The latest computer models for the first half of May project a dip in the jet stream in the West, which tends to result in warm, humid air being pumped northward to the Eastern United States:

Longer-range models for the back half of May are showing less warmth, but they still lean toward a wetter-than-normal pattern.

Despite toasty conditions this week (highs are predicted to be near 90 again Thursday!), the relaxation of the warm pattern should keep this May from being the hottest on record.

April recap

The very warm end to April boosted the month’s average temperature to 60.5 degrees, which is 2.3 degrees higher than normal and the 10th-warmest on record.

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Our dry second half of the month held rainfall to only 2.06 inches, which was 1.15 inches drier than normal.

On April 1, we correctly projected the temperature would average between 60 and 62 degrees, but our forecast rainfall of 4 to 5 inches was much too high.

Here is how the month played out:

All of April’s records were set at the month’s end. Baltimore hit a record high of 92 on Monday, surpassing the previous mark of 91 from 1974. Dulles International Airport set record highs on both Monday and Tuesday, reaching 91 and 88 degrees (surpassing the marks of 89 from 2017 and 86 from 1974, respectively).

This year, so far, is the fourth-warmest on record through April. All but one of the top five warmest years to date are from 2012 or later.

Despite the rainfall deficit in April, this year so far still has a precipitation surplus. We are running about 5 inches wetter than last year up to this point:

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