September Outlook: Warmer Nationwide, With One Big Exception

September 1 marks the first day of the meteorological fall. What does Mother Nature have in store for the weather this month in the U.S., and how will a strengthening El Niño impact what you normally expect to see during the first month of the fall season? We have all of the details for you here.

September's Temperature Outlook

A new long-range outlook released by Atmospheric G2 and The Weather Company is signaling that above-average temperatures will be the story for much of the country. The greatest departure from normal is forecast to stretch across the nation's mid-section from North Dakota to the south through the Plains states and into Texas. Temperatures will hover well above average readings in cities such as Omaha, Kansas City, Tulsa, Oklahoma City, and Dallas.

It will be warmer than usual throughout the Gulf Coast, the Mississippi Valley, the Ohio Valley, and the Great Lakes. It will also be warmer than what you would normally expect for the Rocky Mountain region and the mid-Atlantic.

Temperatures will trend just slightly warmer for the Desert Southwest and the Northeast. While the anticipated readings are still expected to hit above normal, the departure from average will be significantly less dramatic than what is expected for the Plains.

The only corner of the country that is expected to be cooler than usual is the Pacific Northwest. Although the noticeable decline in temperatures may be a bummer to those wanting to hold on to summer a little longer, the cooldown will provide relief to fire crews that have been dealing with a brutal wildfire season in this corner of the country. Cities such as Seattle, Portland, Boise, and Reno will all experience the slide in temperatures.

Precipitation Predictions for September

The historically potent El Niño phase will also influence precipitation expectations throughout the month of September. When compared to averages, the Four Corners region will be the soggiest. An active North American monsoon persisting through the end of the month will drive the rainfall patterns. This will result in a wetter-than-average stretch of weeks for cities such as Los Angeles, San Diego, Phoenix, and Las Vegas.

The interior portions of the West, the northern Rockies, the Great Basin, and much of the Plains will also see more rain than is typically recorded in September. This zone includes Salt Lake City, Denver, Albuquerque, Kansas City, Omaha, St. Louis, Oklahoma City, and Dallas.

Where are conditions expected to be drier? The coastal areas of the Pacific Northwest will continue to experience abnormally dry conditions to pair with the cooler temperatures.

It will also be drier along the East Coast and into the southeastern U.S. The Great Lakes region, the Northeast, and Florida will also see precipitation totals trend below normal.

It is clear that the strong El Niño is exerting significant influence on the fall weather already. The 2026 El Niño is already outpacing the powerful 1997 and 2015 El Niño years in its power and influence.

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