| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Monday, 07-Sep-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Clear in the evening, becoming fair to partly cloudy after midnight. Low 64°. Wind east-southeast around 4 mph, gusting to 22 mph. |
| Tuesday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Very hot. High 94°. UV index up to 7. Wind southeast around 4 mph, gusting to 23 mph. |
| Tuesday night |
Fair to partly cloudy in the evening, becoming clear after midnight. Low 67°. Wind south-southeast around 5 mph, gusting to 17 mph. |
| Wednesday |
Partly cloudy. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely. Very hot. High 95°. Heat index up to 100°. UV index up to 7. Wind south-southwest around 6 mph, gusting to 21 mph, in the morning, becoming west-southwest in the afternoon. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Wednesday night |
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Moderate fog. Rain likely. Scattered thunderstorms likely. Warm. Low 73°. Wind south-southwest around 3 mph in the evening, becoming west-southwest after midnight. Chance of precipitation 80 percent. Precipitation mostly around an inch. |
| Thursday |
Dense overcast in the morning, becoming mostly cloudy to cloudy in the afternoon. Light to moderate fog in the morning. Rain likely in the morning, then a chance of rain in the afternoon. Thunderstorms very likely, some possibly severe. High 80°. Wind northwest around 4 mph, gusting to 19 mph. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch. |
| Thursday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A slight chance of rain. Low 68°. Wind north-northeast around 3 mph, gusting to 16 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. High 82°. UV index up to 5. Wind east around 4 mph, gusting to 19 mph. |
| Friday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog. Low 69°. Wind east-southeast around 4 mph in the evening, becoming south-southeast after midnight. |
| Saturday |
Partly to mostly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain. Scattered thundershowers possible. Warm. High 84°. UV index up to 5. Wind southwest around 3 mph, gusting to 16 mph, in the morning, becoming northwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. Low 70°. Wind east around 2 mph. |
| Sunday |
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 88°. Heat index up to 95°. UV index up to 6. Wind southeast around 5 mph, gusting to 20 mph, in the morning, becoming south in the afternoon. |
| Sunday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Patchy light fog after midnight. A slight chance of rain. Scattered thundershowers possible. Warm. Low 74°. Wind south around 4 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
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