| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Wednesday, 05-Aug-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Light to moderate fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Scattered thunderstorms likely. Low 71°. Wind south-southwest around 2 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch. |
| Thursday |
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning, then patchy light fog in the afternoon. Rain likely in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely. High 84°. UV index up to 8. Wind south-southeast around 3 mph, gusting to 18 mph. Chance of precipitation 80 percent. Precipitation mostly around half an inch. |
| Thursday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog in the evening, then moderate fog after midnight. Rain likely. Scattered thunderstorms likely. Low 73°. Wind southeast around 4 mph, gusting to 16 mph. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Friday |
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. Rain likely. Scattered thunderstorms likely. High 86°. Heat index up to 93°. UV index up to 6. Wind southwest around 5 mph, gusting to 19 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch. |
| Friday night |
Fair in the evening, becoming fair to partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain. Scattered thundershowers possible. Low 73°. Wind southwest around 2 mph in the evening, becoming 5 mph after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Sunny. Light to moderate fog in the morning. Hot. High 92°. Heat index up to 102°. UV index up to 8. Wind west-southwest around 3 mph, gusting to 21 mph, in the morning, becoming south-southwest in the afternoon. |
| Saturday night |
Fair to partly cloudy in the evening, becoming fair after midnight. Patchy light fog in the evening, then moderate fog after midnight. Low 73°. Wind southeast around 5 mph in the evening, becoming south after midnight. |
| Sunday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. Hot. High 94°. Heat index up to 104°. UV index up to 7. Wind west-southwest around 6 mph, gusting to 22 mph. |
| Sunday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 74°. Wind south around 6 mph. |
| Monday |
Sunny in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 95°. Heat index up to 106°. UV index up to 8. Wind south around 7 mph, gusting to 24 mph. |
| Monday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. A slight chance of rain. Scattered thunderstorms likely. Low 75°. Wind south around 6 mph, gusting to 16 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday |
Partly cloudy. Patchy light fog in the morning. A chance of rain. Scattered thunderstorms likely. Hot. High 92°. Heat index up to 104°. UV index up to 8. Wind south-southwest around 6 mph, gusting to 19 mph, in the morning, becoming 9 mph, gusting to 22 mph, in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Mostly cloudy to cloudy. Light to moderate fog in the evening, then moderate fog after midnight. Rain likely in the evening, then a chance of rain after midnight. Thunderstorms very likely, some possibly severe. Low 77°. Wind south-southeast around 8 mph, gusting to 20 mph, in the evening, becoming 3 mph after midnight. Chance of precipitation 80 percent. Precipitation mostly around half an inch. |
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