| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 11-Aug-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Partly to mostly sunny. A chance of rain. Scattered thunderstorms likely. Very hot. High 98°. Heat index up to 112°. UV index up to 8. Wind southwest around 7 mph, gusting to 27 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Tonight |
Fair to partly cloudy. Warm. Low 79°. Wind southwest around 5 mph, gusting to 20 mph. |
| Wednesday |
Partly cloudy. A chance of rain. Scattered thunderstorms likely, some possibly severe. Very hot. High 96°. Heat index up to 111°. UV index up to 8. Wind southwest around 7 mph, gusting to 25 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Wednesday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain. Scattered thunderstorms likely. Warm. Low 78°. Wind south-southeast around 3 mph in the evening, becoming southwest after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday |
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. A chance of rain. Scattered thunderstorms likely, some possibly severe. Hot. High 94°. Heat index up to 107°. UV index up to 7. Wind northeast around 4 mph, gusting to 22 mph, in the morning, becoming south-southeast in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 76°. Wind east-southeast around 4 mph, gusting to 17 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Partly cloudy. Patchy light fog in the morning. Very hot. High 95°. Heat index up to 106°. UV index up to 7. Wind east-southeast around 4 mph, gusting to 23 mph. |
| Friday night |
Clear in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 73°. Wind southeast around 6 mph, gusting to 20 mph. |
| Saturday |
Sunny. Patchy light fog in the morning. Very hot. High 99°. Heat index up to 109°. UV index up to 8. Wind south-southwest around 6 mph, gusting to 22 mph. |
| Saturday night |
Clear. Low 73°. Wind southeast around 4 mph in the evening, becoming south after midnight. |
| Sunday |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Very hot. High 101°. Heat index up to 108°. UV index up to 9. Wind southwest around 9 mph, gusting to 27 mph, in the morning, becoming west in the afternoon. |
| Sunday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Light to moderate fog after midnight. A chance of rain. Scattered thundershowers possible. Low 71°. Wind north-northeast around 5 mph, gusting to 16 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Sunny in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. Hot. High 91°. Heat index up to 96°. UV index up to 8. Wind northeast around 7 mph, gusting to 25 mph. |
| Monday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. Low 68°. Wind east around 5 mph, gusting to 22 mph. |
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