| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 08-Sep-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Very hot. High 92°. UV index up to 6. Wind south-southeast around 4 mph, gusting to 21 mph. |
| Tonight |
Fair in the evening, becoming mostly clear after midnight. Low 65°. Wind south-southeast around 5 mph. |
| Wednesday |
Partly cloudy. A chance of rain. Scattered thundershowers possible. Extremely hot. High 98°. UV index up to 7. Wind west-southwest around 7 mph, gusting to 23 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday night |
Mostly cloudy. Moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Precipitation showery or intermittent. Low 70°. Wind east-southeast around 3 mph in the evening, becoming northwest after midnight. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Thursday |
Partly to mostly cloudy in the morning, becoming mostly cloudy in the afternoon. Moderate fog in the morning. Rain likely. High 80°. UV index up to 4. Wind west-northwest around 4 mph, gusting to 19 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
| Thursday night |
Partly cloudy. Patchy light fog. Low 67°. Wind north around 3 mph, gusting to 16 mph. |
| Friday |
Partly to mostly cloudy in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. Warm. High 85°. UV index up to 6. Wind east-northeast around 4 mph, gusting to 21 mph, in the morning, becoming southeast in the afternoon. |
| Friday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 68°. Wind east-southeast around 5 mph, gusting to 16 mph, in the evening, becoming south-southeast after midnight. |
| Saturday |
Partly to mostly cloudy. Patchy light fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Hot. High 87°. Heat index up to 93°. UV index up to 6. Wind south-southwest around 5 mph, gusting to 19 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday night |
Partly cloudy. Patchy light fog after midnight. Low 68°. Wind west around 2 mph in the evening, becoming north-northwest after midnight. |
| Sunday |
Mostly cloudy to cloudy in the morning, becoming mostly cloudy in the afternoon. Patchy light fog in the morning. Hot. High 86°. UV index up to 5. Wind northeast around 4 mph, gusting to 18 mph, in the morning, becoming south-southwest in the afternoon. |
| Sunday night |
Partly cloudy. Patchy light fog. A chance of rain. Scattered thundershowers possible. Low 67°. Wind south-southwest around 3 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Partly to mostly cloudy in the morning, becoming sunny in the afternoon. Very hot. High 94°. Heat index up to 102°. UV index up to 7. Wind southwest around 7 mph, gusting to 20 mph, in the morning, becoming 11 mph, gusting to 23 mph, in the afternoon. |
| Monday night |
Mostly clear in the evening, becoming fair after midnight. Patchy light fog after midnight. Warm. Low 72°. Wind southwest around 5 mph, gusting to 15 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.