| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 04-Aug-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. High 89°. UV index up to 9. Wind south around 4 mph, gusting to 22 mph. |
| Tonight |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Light to moderate fog after midnight. A chance of rain. Relatively cool. Low 66°. Wind southeast around 5 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. High 88°. UV index up to 8. Wind south-southeast around 5 mph, gusting to 19 mph, in the morning, becoming southwest in the afternoon. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Wednesday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. Rain likely. Scattered thundershowers possible. Low 70°. Wind northeast around 2 mph in the evening, becoming south-southeast after midnight. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch. |
| Thursday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. Rain likely. Scattered thundershowers possible. High 86°. Heat index up to 93°. UV index up to 8. Wind south-southwest around 4 mph, gusting to 20 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
| Thursday night |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thunderstorms likely. Low 74°. Wind south-southeast around 4 mph, gusting to 16 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Friday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. High 89°. Heat index up to 95°. UV index up to 7. Wind west-southwest around 5 mph, gusting to 22 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Fair. Patchy light fog in the evening, then light to moderate fog after midnight. Low 73°. Wind south-southwest around 3 mph, gusting to 15 mph. |
| Saturday |
Partly cloudy in the morning, becoming sunny in the afternoon. Light to moderate fog in the morning. Hot. High 91°. Heat index up to 100°. UV index up to 8. Wind southwest around 4 mph, gusting to 21 mph. |
| Saturday night |
Clear in the evening, becoming mostly clear after midnight. Moderate fog after midnight. Low 73°. Wind south around 4 mph, gusting to 17 mph. |
| Sunday |
Sunny. Light to moderate fog in the morning. Hot. High 95°. Heat index up to 105°. UV index up to 8. Wind south-southwest around 6 mph, gusting to 21 mph. |
| Sunday night |
Clear. Low 74°. Wind south-southwest around 7 mph, gusting to 15 mph. |
| Monday |
Sunny in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 97°. Heat index up to 107°. UV index up to 9. Wind south-southwest around 8 mph, gusting to 22 mph. |
| Monday night |
Partly cloudy in the evening, becoming fair after midnight. Low 75°. Wind south-southwest around 7 mph, gusting to 17 mph. |
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