Weather across America 9/21/2025

(NATIONAL) Clusters of thunderstorms will continue across portions of the Midwest southwest through the central/southern Plains with a threat for flash flooding and severe weather, scattered showers and thunderstorms will arrive again across the Southwest along with a threat for isolated areas of flash flooding, and above average temperatures are expected across much of the central and eastern U.S., with near to slightly below average temperatures across the West as Summer draws to a close.

Unsettled weather is expected to continue across much of the Midwest and Ohio/Tennessee Valleys west through the Mississippi Valley and into the central/southern Plains this weekend and into early next week. An energetic slow-moving upper-trough and associated surface frontal/convective boundaries will help to trigger additional rounds of showers and thunderstorms, with a continuous flow of Gulf moisture helping to support an upward trend in heavy rainfall chances in each of the coming days. Clustering of storms along frontal/convective boundaries will bring a greater chance for repeated rounds of heavy rainfall.

For Sunday, the most likely area to see heavy rainfall and scattered instances of flash flooding is centered on the MO/KS/AR/OK border region, with a Slight Risk of Excessive Rainfall (level 2/4) now in effect. More isolated instances of flash flooding will also be possible from the Middle Mississippi Valley southwest through the Ozarks and into portions of the central/southern Plains. Then, on Monday, the most likely region to see isolated flash flooding will stretch from the Ohio Valley west through the Mid-South into the Ozarks vicinity and portions of the central/southern Plains.

Additional areas and potentially higher levels of threat are possible with more confidence in convective trends and associated boundary locations. A more concentrated, greater threat for scattered flash flooding is already expected across the Ozarks and vicinity on Tuesday, with another Slight Risk of Excessive Rainfall (level 2/4) in effect. Elsewhere, daily thunderstorms can be expected across central/southern Florida as well as along the western Gulf Coast.

A return of Monsoonal moisture into the Desert Southwest ahead of an upper-low over the Pacific will bring increased thunderstorm chances Sunday and Monday. Locally heavy downpours will be possible, and an isolated flash flood threat will exist especially for the Colorado River Valley into central Arizona Sunday, and expanding east into western New Mexico on Monday. To the north, a cold front moving into the Pacific Northwest will continue to bring shower chances Sunday, with showers and thunderstorms also spreading eastward into portions of the northern Great Basin and Rockies.

Storm chances will continue further southeastward into the central Rockies by Monday. Much of the central and eastern U.S. will continue to see above to well above average temperatures for the last couple days of Summer. Highs in the upper 80s to mid-90s will be common across the Southeast, Lower Mississippi Valley, and into the southern Plains/Texas, with 70s and 80s for the Midwest west through the central/northern Plains.

Some locally hotter temperatures in the mid-80s to around 90 will be possible across portions of the Ohio Valley/Lower Great Lakes as well as the northern High Plains on Sunday. Portions of the Northeast, especially east of the Appalachians, will remain cooler and generally in the low 70s Sunday with a warming trend into the mid- to upper 70s on Monday.

Much of the West will see temperatures around or below average, with highs in the 60s and 70s for the Pacific Northwest; the 70s and 80s for the Great Basin, Rockies vicinity, and California; and 90s to low 100s in the Desert Southwest. A warming trend will bring temperatures into 90s for the central California Valleys and 80s northward into portions of the inland Pacific Northwest by Monday.