"Polar air" is set to surge southward this week, plunging temperatures below normal as far south as Arkansas, Tennessee and Mississippi, with AccuWeather meteorologists predicting the weather will feel more like mid-October for about 250 million people.
Why It Matters
September 1 marks the first day of meteorological fall, although the autumnal equinox doesn't officially begin until September 22. The end of summer has brought contrasting weather across the country. A cold front ushered in below-average temperatures in many states last week, dropping temperatures as far as 30 degrees below average for parts of the central and southern Plains, including Texas. Meanwhile, abnormally high temperatures have persisted across the Pacific Northwest and parts of Alaska, prompting heat-related weather alerts.
This week is again expected to bring chilly temperatures to much of the U.S., described as "blustery" for some northern states.
What To Know
On Monday, AccuWeather meteorologists updated a forecast showing that temperatures more likely in mid-October is expected to stretch across a wide swath of the U.S.
The cold weather is set to affect northern states such as North Dakota and Michigan and stretch as far south as Oklahoma east through parts of North Carolina.
The cold temperatures begin earlier in the week for the northern parts of the U.S. and descend across the country until they reach the southern states by Thursday afternoon.
"On the chilliest days, highs in the northern tier of the Midwest and higher elevations of the Appalachians may hold in the 40s," the AccuWeather report said. "Farther south and east, highs will range from the 50s and 60s across the central Plains and Ohio Valley to the 70s and low 80s from the southern Plains to the central Gulf Coast, accompanied by some of the lowest humidity levels since last fall or winter."
Parts of the Midwest and interior Northeast could see overnight temperatures dip as low as the 30s. In the southern Plains and interior Southeast, nighttime temperatures are expected to dip as low as the 40s.
From Tennessee north, temperatures could be as much as 20 degrees below normal. Despite the low temperatures, AccuWeather senior meteorologist Tom Kines told Newsweek he doesn't expect any records to be broken by the chilly weather.
"But no doubt it's below normal," he said, adding that some places across the northern U.S. can expect to see their first frost.
AccuWeather anticipates the jet stream will lift northward once again by next weekend, causing an area of high pressure to stretch across Eastern states.
"If that occurs, many of the same areas experiencing the chill could shift back to a midsummerlike pattern with higher humidity and highs in the 80s to near 90 for a few days," the forecast said.
What People Are Saying
The National Weather Service St. Louis wrote on X on Sunday: "If you enjoy fall temperatures you are in for another treat. Well-below normal values are on track beginning on THU behind a strong cold front. Highs in the 60s for many locations w/ lows in the 40s are expected."
NWS Burlington, Vermont, wrote on X: "Enjoy the fall-like start to September!"
What Happens Next
Below-average temperatures will likely persist across the central, Midwestern and Northeastern U.S. through September 10, according to temperature outlooks from the NWS's Climate Prediction Center. Looking further out, above-average temperatures are set to return to much of the U.S. between September 8 and 14.
Update 9/1/2025, 12:32 p.m. Eastern time: This article was updated to include comment from AccuWeather.
