Meteorological autumn starts Sept. 1, with the astronomical equinox arriving at 8:05 p.m. EDT on Sept. 22, but summer warmth is set to hold its ground across much of the United States for weeks longer than usual.
According to AccuWeather’s 2026 fall forecast, an intensifying El Niño pattern in the eastern Pacific Ocean will serve as the primary driver of weather conditions across the nation throughout the coming months.
“A very strong El Niño will be a dominant signal through the fall,” said Paul Pastelok, lead long-range expert at AccuWeather.
El Niño occurs when equatorial Pacific waters warm above historical averages, shifting global jet streams and storm tracks. Forecasters note that this year’s event could become one of the strongest on record. Other localized factors, including unusually warm waters in the northern Pacific and the Gulf of Mexico, alongside lingering pockets of extreme drought, will interact with the El Niño pattern to shape regional weather.
September is expected to feel like an extension of summer, particularly in the Southeast and Mid-Atlantic, where high humidity and warm nights will persist. Initial cold fronts arriving in the Great Lakes, Northeast, and north-central Plains during October are projected to be brief.
Drought conditions in the interior Northwest, Rockies, and Mid-Atlantic could keep wildfire risks elevated into early autumn. However, forecasters note that sunny days paired with cooler October nights may still yield bright fall foliage across parts of the Midwest and Northeast.
Despite El Niño typically suppressing Atlantic hurricane activity, coastal regions remain vulnerable. Two tropical storms, Arthur in June and Bertha in July, have already made landfall along the Gulf Coast this year.
“In the Atlantic basin, El Niño may hold back the number of named storms in 2026, but there can still be several impacts on the United States,” Pastelok said.
Areas at elevated risk for tropical impacts this season include the northern and eastern Gulf Coast, the Carolinas, and portions of southern New England.
Severe thunderstorm risks are projected to shift from the Midwest and northern Plains toward the southern Plains, the Tennessee Valley, and the Gulf Coast as autumn progresses. Warm Gulf moisture is expected to fuel heavy rainfall and heighten flood potential across the South during the second half of the season.
“Reduced Atlantic tropical activity may result in fewer tropical cyclone-related tornadoes across the Southeast,” said Alex Duffus, AccuWeather severe weather expert.
In the West, late-monsoon rainfall may offer brief drought relief to Arizona, Southern California, and southern Nevada during September, though atmospheric river events remain possible in California later in the season.
Snowfall is expected to remain largely restricted to high mountain elevations through October. The highest peaks of the Rockies in Idaho, Wyoming, and Montana may see early accumulation in late September, while snow in the Cascades may be delayed due to warmer initial temperatures.
Chance for snow across populated areas in the Northeast, Great Lakes, and lower elevations of the Rockies will increase heading into November. Pastelok noted that a single cold system mixing with moisture late in October or early in November could trigger early snow for parts of the Northeast, alongside typical lake-effect snow downwind of the Great Lakes in November.
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