| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Wednesday, 19-Aug-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair to partly cloudy. Light to moderate fog in the evening, then moderate fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 70°. Wind east-northeast around 3 mph, gusting to 15 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Thursday |
Partly to mostly sunny. Moderate fog in the morning. A chance of rain. High 84°. UV index up to 7. Wind northeast around 5 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Thursday night |
Fair to partly cloudy in the evening, becoming fair after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A slight chance of rain. Low 67°. Wind northeast around 3 mph, gusting to 16 mph, in the evening, becoming east after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Light to moderate fog in the morning. A chance of rain. High 85°. UV index up to 7. Wind south around 2 mph, gusting to 19 mph, in the morning, becoming west-southwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Mostly clear in the evening, becoming fair after midnight. Patchy light fog after midnight. Low 69°. Wind west-southwest around 2 mph in the evening, becoming west-northwest after midnight. |
| Saturday |
Sunny. Patchy light fog in the morning. Hot. High 87°. Heat index up to 92°. UV index up to 7. Wind north-northwest around 4 mph, gusting to 22 mph. |
| Saturday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 66°. Wind north-northeast around 3 mph, gusting to 17 mph, in the evening, becoming north-northwest after midnight. |
| Sunday |
Partly cloudy. Patchy light fog in the morning. High 85°. UV index up to 7. Wind east-northeast around 4 mph, gusting to 23 mph, in the morning, becoming north-northwest in the afternoon. |
| Sunday night |
Fair to partly cloudy in the evening, becoming fair after midnight. Patchy light fog after midnight. Low 63°. Wind north-northwest around 2 mph, gusting to 15 mph, in the evening, becoming east-northeast after midnight. |
| Monday |
Partly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. High 85°. UV index up to 7. Wind east around 5 mph, gusting to 23 mph. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Monday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Precipitation showery or intermittent. Low 67°. Wind east around 6 mph, gusting to 15 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday |
Partly cloudy. Moderate fog in the morning. High 86°. UV index up to 8. Wind east around 6 mph, gusting to 23 mph. |
| Tuesday night |
Partly cloudy. Patchy light fog after midnight. Low 67°. Wind east around 3 mph, gusting to 16 mph. |
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