| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Sunday, 26-Jul-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. Very hot. High 99°. Heat index up to 110°. UV index up to 9. Wind southwest around 3 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tonight |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog after midnight. A chance of rain. Scattered thundershowers possible. Low 76°. Wind west-southwest around 3 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Partly cloudy in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain. Scattered thunderstorms likely. Very hot. High 97°. Heat index up to 111°. UV index up to 9. Wind southwest around 6 mph, gusting to 22 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Partly cloudy in the evening, becoming fair after midnight. Light to moderate fog after midnight. A chance of rain. Scattered thundershowers possible. Low 78°. Wind southwest around 5 mph, gusting to 17 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 96°. Heat index up to 108°. UV index up to 9. Wind north around 6 mph, gusting to 25 mph. |
| Tuesday night |
Fair in the evening, becoming partly to mostly cloudy after midnight. Low 72°. Wind northeast around 4 mph, gusting to 22 mph. |
| Wednesday |
Partly cloudy in the morning, becoming sunny in the afternoon. Hot. High 91°. Heat index up to 98°. UV index up to 9. Wind east around 4 mph, gusting to 23 mph. |
| Wednesday night |
Clear. Patchy light fog after midnight. Low 68°. Wind east around 4 mph, gusting to 21 mph. |
| Thursday |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 93°. Heat index up to 97°. UV index up to 8. Wind southeast around 4 mph, gusting to 23 mph. |
| Thursday night |
Partly cloudy. Patchy light fog after midnight. A slight chance of rain. Low 69°. Wind east around 5 mph, gusting to 20 mph, in the evening, becoming southeast after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain in the afternoon. Scattered thunderstorms likely. Hot. High 93°. Heat index up to 98°. UV index up to 9. Wind south around 7 mph, gusting to 25 mph, in the morning, becoming west-southwest in the afternoon. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Friday night |
Moderate fog. A chance of rain. Low 70°. Wind north around 8 mph, gusting to 18 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Saturday |
Sunny. Moderate fog in the morning. Breezy. High 86°. UV index up to 9. Wind north-northwest around 9 mph, gusting to 29 mph, in the morning, becoming 13 mph, gusting to 29 mph, in the afternoon. |
| Saturday night |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 69°. Wind north-northwest around 10 mph, gusting to 26 mph, in the evening, becoming 5 mph, gusting to 18 mph, after midnight. |
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