| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Monday, 14-Sep-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Hot. High 85°. UV index up to 6. Wind east-southeast around 8 mph, gusting to 27 mph. |
| Tonight |
Clear in the evening, becoming fair to partly cloudy after midnight. Low 63°. Wind southeast around 8 mph, gusting to 21 mph. |
| Tuesday |
Sunny in the morning, becoming partly cloudy in the afternoon. A chance of rain in the afternoon. Scattered thunderstorms likely. Extremely hot. High 97°. UV index up to 7. Wind south around 6 mph, gusting to 23 mph, in the morning, becoming west-southwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thundershowers possible. Low 68°. Wind southeast around 2 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 sunny in the afternoon. A chance of rain. Scattered thundershowers possible. Very hot. High 93°. Heat index up to 100°. UV index up to 6. Wind southeast around 3 mph, gusting to 20 mph, in the morning, becoming south-southwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday 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. Warm. Low 70°. Wind south around 3 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday |
Mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Very hot. High 93°. Heat index up to 101°. UV index up to 5. Wind west-southwest around 4 mph, gusting to 19 mph, in the morning, becoming west-northwest in the afternoon. |
| Thursday night |
Partly cloudy. Patchy light fog after midnight. Low 68°. Wind north around 2 mph. |
| Friday |
Mostly sunny. Patchy light fog in the morning. Very hot. High 92°. Heat index up to 98°. UV index up to 7. Wind east-northeast around 3 mph, gusting to 17 mph, in the morning, becoming southeast in the afternoon. |
| Friday night |
Partly cloudy in the evening, becoming mostly clear after midnight. Light to moderate fog after midnight. A slight chance of rain. Scattered thundershowers possible. Low 68°. Wind southeast around 4 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Sunny. Patchy light fog in the morning. Very hot. High 96°. Heat index up to 101°. UV index up to 7. Wind south-southwest around 6 mph, gusting to 21 mph. |
| Saturday night |
Partly cloudy in the evening, becoming fair after midnight. Light to moderate fog. A chance of rain. Scattered thundershowers possible. Warm. Low 69°. Wind south around 3 mph. Chance of precipitation 50 percent. Precipitation mostly around a quarter of an inch. |
| Sunday |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 92°. Heat index up to 98°. UV index up to 6. Wind southwest around 7 mph, gusting to 24 mph. |
| Sunday night |
Partly to mostly cloudy. Moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 69°. Wind west around 3 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
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