Mild May? Enjoy cool weather while it lasts, forecasters say.
A chillier-than-usual May is in store for much of the eastern half of the country. But summer isn't far behind.
Jeanine SantucciIt’s the calm before the storm – for the temperature, that is.
After an early spring marked by ups and downs in temperature trends, forecasters say much of May will be cooler than normal for most of the country, ahead of what could be a summer of coast-to-coast heat.
The cooldown will be most pronounced in the Midwest, said the Climate Prediction Center’s meteorologist Brad Pugh. In that region, there could even be some overnight lows that dip into frosting or freezing territory, he said.
For most of the eastern half of the United States, at least the first part of the month will feel more like early spring, AccuWeather Lead Long-Range Expert Paul Pastelok said. During that time, there may be some sunny days, but “more times than not, we’re going to have a lot of clouds during the day,” Pastelok said.
The notable exception to the cooling trend is the West Coast, especially the Pacific Northwest, which is getting an early start to above-average temperatures. The transition to summer-like temperatures there will be much quicker than the rest of the nation, and during the course of May, the warmth will spread from West to East as summer approaches, Pastelok said.
“In the East it’ll feel more like late March, early April than early May... we still need our jackets, we still need our sweaters,” he said. “But in the Northwest, it’s time to get to the summer outfit.”
Cool May will shift to coast-to-coast hot summer
The cool pattern in the eastern part of the country is thanks to a dip in the jet stream lingering over the United States, while atmospheric blocking prevents it from heading northward to Canada, Pastelok said.
Once we get into about the third week of May, that blocking won’t be as strong, and the cool air will shift away, he said.
Several major cities, including places like Detroit, Pittsburgh and New York City, could see temperatures of an average of 2 to 4 degrees below normal for the month of May, Pastelok said. That may not sound like much, but when taken over a 30-day period, 2 to 4 degrees is a significant departure from a typical May, he said.
On a day-to-day basis, temperatures could be as much as 15 degrees below average in eastern cities, he said.
In New York City, for example, a normal May would see temperatures in the upper 60s early in the month to mid 70s later in the month. But this year, temperatures will likely stay in the 60s or even upper 50s, with lows dropping down into the 40s.
Chicago’s usual highs in May range similarly from the 60s to mid 70s, but this year, the first part of May will see days 10 to 15 degrees below average with highs in the 50s, Pastelok said. By mid month, the warmup moving west to east will have reached Chicago and temperatures will be more average to even above average by late May.
In the East, that transition to summer with higher temperatures and humidity will be much more gradual through June than it will be in the West, Pastelok said. That may be bad news for those who want to get into the pool early in the morning in June, but it’s great news for those wanting to relax by a bonfire in the evenings, he said.
The Climate Prediction Center outlook from May to July on the whole shows chances that lean toward above normal, with areas in the Northwest and some in the South and Mid-Atlantic with higher chances.
“Our May, June, July outlook calls for an increased chance of above-normal temperatures for the majority of the country,” Pugh said.
AccuWeather predicts a “summer of weather extremes,” from heat waves in the West and South, repeated thunderstorms risking flash flooding from Texas to the Ohio Valley and worsening drought in the Northwest and Great Basin.
“The nation could be divided by weather extremes this summer,” Pastelok said. “We may see dramatically different conditions happening at the same time, with flash flooding in one region while others deal with extreme heat, drought and wildfires.”
May could bring frost, freeze to some areas
In the Midwest, particularly around the Great Lakes and Upper Mississippi Valley, temperatures will likely be 5 to 10 degrees below average in the first part of May, Pugh said. On May 1, early morning lows got to the freezing point in states like Wisconsin, he said.
Frost or freeze could return to the area around May 7 and 8, Pugh said.
Other areas that could see chilly enough overnight lows include the Mid-Atlantic and New England, Pastelok said.
Above-normal temperatures to start early in the Northwest
In the West, temperatures have already begun to warm. East of the Cascades in cities like Spokane, Washington, there may be a couple days straight of temperatures 10 to 15 degrees above average, and the warming will spread down to Nevada, Utah, Arizona and California, Pastelok said.
Spokane’s high temperature on May 3 is forecast to be 80 degrees, and 79 on May 4.
In the Great Basin region, up through Boise, Idaho, highs in the 70s into the 80s and even a couple of 90s days are possible by the end of May, Pastelok said. After not having much a snow pack in the Central Rockies, the fast drying and heating process as summer ramps up is “very dangerous for fire season,” he said.
“It’ll feel more like late June than early May at times,” Pastelok said, adding that many heat records could be broken in the Northwest as the summer gets underway.