The Southeast will also generally see above-average conditions, with areas into parts of the mid-Atlantic and Ohio Valley likely to see near-average or slightly above-average temperatures.

May 2019 temperature outlook from The Weather Company, an IBM Business.

Below-average temperatures, however, are anticipated from parts of the northern Plains into the northern Great Lakes and northern New England. The central U.S. and the Northeast is expected to experience near or slightly-below-average temperatures.

In April, the central U.S. has seen periods of below-average temperatures, and this trend may continue into May.

"We've made further cooler changes to the May forecast across the northern Plains into the Northeast U.S. given reasonably strong agreement between the medium-range models and the various statistical and climate model forecasts for May," said Dr. Todd Crawford, chief meteorologist at The Weather Company.

The medium-range models show an upper-level pattern that will be favorable for chilly conditions across much of the northern tier of the U.S. through at least early May.

Crawford also noted that there are indications that a more sustained flow of colder air will be found in the northern U.S. in May compared to April.

Keep in mind, this is the overall average trend for the month, and an individual cold front or an upper ridge of high pressure can lead to a period of colder or warmer weather, respectively.

May's Average Temperatures

Temperatures average in the 80s across the South in May, which suggests above-average temperatures in the Southeast could be very warm. However, those in the southern Plains, where slightly cooler-than-average temperatures are possible, might get a break from the heat.

Average highs across the northern tier are in the 60s in May, so there could be a cool feel to the month in areas where below-average temperatures emerge.

Average high temperatures in May.

Morning lows can still be chilly in May, especially in parts of the higher elevations of the West, as well as from northeastern Minnesota into far northern New England, where lows average in the 30s. 

Colder-than-average temperatures from the upper Midwest to northern New England could lead to more of a winter or early-spring feel at times. However, above-average temperatures in the West may result in a mild start to the day.

Average lows are in the 50s and 60s across the South, and warmer-than-average conditions there would make it feel more like summer than late spring.

Average low temperatures in May.