| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 23-Jun-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Relatively cool. Low 65°. Wind east around 4 mph, gusting to 23 mph, in the evening, becoming south-southeast after midnight. |
| Wednesday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. High 84°. UV index up to 7. Wind south-southeast around 5 mph, gusting to 23 mph, in the morning, becoming southwest around 8 mph, gusting to 27 mph, in the afternoon. 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 moderate fog after midnight. Low 66°. Wind west around 4 mph, gusting to 24 mph. |
| Thursday |
Partly to mostly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. Patchy light fog in the morning, then light to moderate fog in the afternoon. A slight chance of rain in the morning, then rain likely in the afternoon. Scattered thunderstorms likely. High 86°. UV index up to 7. Wind west around 4 mph, gusting to 23 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Thursday night |
Cloudy in the evening, becoming dense overcast after midnight. Light to moderate fog in the evening, then patchy light fog after midnight. Rain very likely. Scattered thundershowers possible. Low 69°. Wind east around 3 mph in the evening, becoming south-southeast after midnight. Chance of precipitation 80 percent. Precipitation mostly between half an inch and one inch. |
| Friday |
Dense overcast in the morning, becoming cloudy in the afternoon. Light to moderate fog in the morning, then moderate fog in the afternoon. Rain very likely. Scattered thundershowers possible. Relatively cool. High 72°. UV index up to 4. Wind east-southeast around 4 mph. Chance of precipitation 80 percent. Precipitation mostly between 1 and 2 inches. |
| Friday night |
Cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Moderate fog. Rain likely. Scattered thunderstorms likely. Low 68°. Wind north-northeast around 3 mph in the evening, becoming south-southwest after midnight. Chance of precipitation 80 percent. Precipitation mostly between 1 and 2 inches. |
| Saturday |
Partly to mostly cloudy. Moderate fog in the morning. A chance of rain. Scattered thunderstorms likely. High 86°. Heat index up to 92°. UV index up to 7. Wind south-southwest around 4 mph, gusting to 20 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Saturday night |
Partly cloudy. Moderate fog. Rain likely. Scattered thunderstorms likely. Low 73°. Wind south-southeast around 4 mph in the evening, becoming southwest after midnight. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Sunday |
Partly to mostly sunny in the morning, becoming mostly sunny in the afternoon. Moderate to dense fog in the morning. Hot. High 90°. Heat index up to 101°. UV index up to 9. Wind south-southeast around 6 mph, gusting to 21 mph. |
| Sunday night |
Clear. Light to moderate fog in the evening, then moderate to dense fog after midnight. Low 74°. Wind south around 5 mph, gusting to 17 mph. |
| Monday |
Sunny. Moderate fog in the morning. Hot. High 93°. Heat index up to 105°. UV index up to 10. Wind south around 5 mph, gusting to 18 mph, in the morning, becoming southwest in the afternoon. |
| Monday night |
Mostly clear in the evening, becoming mostly cloudy to cloudy after midnight. Patchy light fog. Low 76°. Wind southeast around 2 mph in the evening, becoming south-southwest after midnight. |
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