May 2021 Temperature Outlook: Warmer Than Average Conditions Anticipated for Eastern, Central U.S.

 Linda Lam

Published: April 30, 2021

Notable changes have been made to the May temperature forecast across the Lower 48, although a very warm May is still expected.

Temperatures will be the greatest above average in parts of the Midwest, South and East, instead of the Plains and Four Corners region, compared to the outlook issued earlier in April.

Parts of the West, particularly the Northwest, are the areas of the contiguous U.S. that may trend near to slightly cooler than average.

(MORE: What May Weather Can Bring)

May Temperature Outlook

"We've made adjustments to the May forecast in line with our current medium-range and sub-seasonal forecasts, and this has resulted in cooler forecast temperatures across most of the western half of the country and warmer temperatures across parts of the eastern U.S.," Todd Crawford, chief meteorologist with The Weather Company, highlighted.

This outlook is driven by a pattern change that is expected to develop in May. The upper-level pattern has been dominated by an amplified jet stream with a northward bulge or ridge in both the North Pacific and the North Atlantic. This pattern should break down in May.

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Also, the evolution of the Madden-Julian Oscillation (MJO), which is an atmospheric disturbance in the tropics that propagates eastward around the globe, signals that very warm conditions will develop during the second half of May over much of the Lower 48.

May's Typical Temperatures

Temperatures in the southern tier of the U.S. typically begin to resemble summer as May progresses. Average highs from the Southeast into the Desert Southwest reach the 80s and 90s. Farther north, average highs climb into the 60s and 70s during May.

A warmer than average May, especially during the second half, suggests it may feel more like summer for much of the central and eastern United States.

Average May Highs

Mild mornings become the rule across the South with lows typically dipping only into the 50s and 60s. Above-average temperatures here indicate that warm, humid mornings may be ahead

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It can still feel chilly in the mornings in May in parts of the West and closer to the Canadian border. Cool mornings will likely dominate the Northwest this May, where near or slightly below average temperatures are anticipated.

Average May Lows

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.