| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Sunday, 09-Aug-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair to partly cloudy. Patchy light fog. A chance of rain. Precipitation showery or intermittent. Low 75°. Wind south-southwest around 7 mph, gusting to 24 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Partly to mostly sunny. Light to moderate fog in the morning. Rain likely. Scattered thundershowers possible. Hot. High 93°. Heat index up to 104°. UV index up to 8. Wind south-southwest around 7 mph, gusting to 23 mph. Chance of precipitation 60 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Partly cloudy. Light to moderate fog after midnight. A chance of rain after midnight. Scattered thundershowers possible. Low 75°. Wind south-southwest around 5 mph, gusting to 16 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday |
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Light to moderate fog in the morning. A chance of rain. Scattered thundershowers possible. Hot. High 94°. Heat index up to 107°. UV index up to 8. Wind southwest around 6 mph, gusting to 22 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Partly cloudy. Patchy light fog after midnight. A chance of rain. Scattered thundershowers possible. Low 77°. Wind southwest around 5 mph, gusting to 16 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Partly cloudy. Patchy light fog in the morning. Very hot. High 98°. Heat index up to 111°. UV index up to 8. Wind southwest around 4 mph, gusting to 23 mph. |
| Wednesday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 76°. Wind south-southwest around 3 mph, gusting to 16 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday |
Partly cloudy. Patchy light fog in the morning. A chance of rain. Scattered thunderstorms likely. Very hot. High 96°. Heat index up to 107°. UV index up to 7. Wind south-southeast around 4 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. A chance of rain. Scattered thunderstorms likely. Low 75°. Wind east-northeast around 4 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Partly cloudy in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. A chance of rain. Scattered thundershowers possible. Very hot. High 96°. Heat index up to 108°. UV index up to 8. Wind east-southeast around 3 mph, gusting to 20 mph, in the morning, becoming south in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Clear. Low 74°. Wind east-southeast around 5 mph in the evening, becoming south-southwest after midnight. |
| Saturday |
Sunny. Extremely hot. High 102°. Heat index up to 111°. UV index up to 9. Wind south-southwest around 9 mph, gusting to 26 mph, in the morning, becoming west-southwest in the afternoon. |
| Saturday night |
Clear. Low 71°. Wind southwest around 8 mph, gusting to 16 mph. |
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