OKLAHOMA CITY, Oklahoma — Two distinct rounds of severe weather are targeting the Plains on Sunday, September 20, 2026, with Oklahoma City and Tulsa facing a focused threat for severe damaging wind gusts by late afternoon and evening while Denver and the Colorado Front Range face supercells capable of large hail and severe wind gusts during the afternoon. A third separate threat stretches along the cold front from the Ozarks eastward into the central Appalachians, bringing a localized risk of gusty winds and hail to communities from St. Louis through Indianapolis, Louisville, Knoxville and Asheville throughout Sunday afternoon. Three separate severe weather zones on a single day demands attention across a wide swath of the country this Sunday.
Round 1: Oklahoma City and Tulsa Face Damaging Wind Gusts Sunday Afternoon and Evening
Central and eastern Oklahoma are in the most focused severe weather zone on Sunday, September 20, 2026, with Oklahoma City and Tulsa both sitting within the Slight Risk zone on the outlook. Here is how the threat develops:
- Intense afternoon heat and humidity ahead of a cold front will fuel strong storm development across central and eastern Oklahoma during the afternoon hours of Sunday, September 20.
- As storms initiate, they are expected to quickly merge into a larger cluster, bringing a focused and organized threat for severe and damaging wind gusts by late afternoon and evening across Oklahoma City, Tulsa and surrounding communities.
- The merging of individual storm cells into a larger cluster is a key signal — cluster-type storm systems are especially efficient at producing widespread straight-line damaging winds across a large area simultaneously, meaning the threat is not limited to isolated spots but could affect a broad swath of central and eastern Oklahoma through Sunday evening.
Round 2: Denver and the Colorado Front Range Face Supercells and Large Hail Sunday Afternoon
Further west, Denver and the Colorado Front Range face a completely separate severe weather threat driven by a different atmospheric mechanism on Sunday, September 20, 2026:
- Upslope winds pushing against the Colorado Front Range will trigger scattered afternoon thunderstorms across the Denver area and surrounding Front Range communities during Sunday afternoon.
- With more favorable wind shear in place, a few of these storms could organize into supercells — rotating thunderstorms capable of producing large hail alongside severe wind gusts.
- Denver sits within the Slight Risk zone on the Sunday, September 20 severe weather outlook, confirming that scattered severe storms including large hail-producing supercells are expected to develop during the afternoon heating hours along the Front Range.
A third and more isolated threat stretches along the cold front from the Ozarks eastward into the central Appalachians on Sunday, September 20, 2026. Cities visible within this Marginal Risk corridor include:
- St. Louis, Missouri falls within the Marginal Risk zone on the Sunday outlook map, with isolated strong storms carrying gusty winds and hail possible during the afternoon.
- Indianapolis, Indiana and Columbus, Ohio are both visible within the Marginal Risk zone on the Sunday, September 20 severe weather outlook.
- Cincinnati, Ohio and Louisville, Kentucky fall within the Marginal Risk zone along the cold front corridor through Sunday afternoon.
- Knoxville, Tennessee and Asheville, North Carolina are visible at the eastern end of the Marginal Risk zone where the cold front pushes into the central Appalachians on Sunday, September 20, 2026.
What Each Risk Zone Means for Your Sunday Plans
- If you live near Oklahoma City or Tulsa, Sunday afternoon and evening outdoor plans carry a genuine severe weather risk. The storms expected to develop and merge by late afternoon could produce damaging wind gusts quickly and with limited additional warning time. Have weather alerts active before heading outside Sunday afternoon.
- If you live near Denver or along the Colorado Front Range, scattered supercells with large hail are possible during peak afternoon heating hours on Sunday, September 20. Move vehicles under cover before afternoon storms develop if possible.
- If you live near St. Louis, Indianapolis, Louisville, Knoxville or Asheville, the threat is more isolated but not zero. Keep weather alerts active throughout Sunday afternoon as the cold front tracks eastward through your area.
