| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Sunday, 21-Jun-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Mostly cloudy to cloudy. Light to moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Low 72°. Wind west-southwest around 6 mph, gusting to 26 mph, in the evening, becoming northwest after midnight. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Monday |
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. High 83°. UV index up to 7. Wind north around 6 mph, gusting to 27 mph. |
| Monday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Relatively cool. Low 64°. Wind north-northeast around 2 mph, gusting to 23 mph. |
| Tuesday |
Mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. High 84°. UV index up to 8. Wind east-northeast around 3 mph, gusting to 22 mph. |
| Tuesday night |
Fair in the evening, becoming partly to mostly cloudy after midnight. A chance of rain after midnight. Relatively cool. Low 62°. Wind east-northeast around 4 mph, gusting to 21 mph, in the evening, becoming east-southeast after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Cloudy. Patchy light fog in the morning. A chance of rain in the morning, then rain likely in the afternoon. Scattered thunderstorms likely. High 77°. UV index up to 5. Wind south around 4 mph, gusting to 18 mph. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch. |
| Wednesday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog. A chance of rain. Scattered thunderstorms likely. Low 67°. Wind west-southwest around 4 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday |
Partly cloudy in the morning, becoming partly to mostly 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 86°. UV index up to 7. Wind north around 3 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Thursday night |
Mostly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain. Scattered thundershowers possible. Low 67°. Wind northeast around 4 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Friday |
Mostly cloudy in the morning, becoming dense overcast in the afternoon. Light to moderate fog. Rain very likely. Scattered thunderstorms likely. Relatively cool. High 73°. Wind east-southeast around 5 mph. Chance of precipitation 90 percent. Precipitation mostly around an inch. |
| Friday night |
Cloudy. Light to moderate fog. Rain likely in the evening, then a chance of rain after midnight. Scattered thunderstorms likely. Low 69°. Wind east-southeast around 5 mph in the evening, becoming north-northeast after midnight. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch. |
| Saturday |
Mostly cloudy to cloudy in the morning, becoming mostly cloudy in the afternoon. Patchy light fog in the morning. Rain likely. Thunderstorms very likely, some possibly severe. High 87°. Heat index up to 93°. UV index up to 6. Wind southwest around 9 mph, gusting to 22 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch. |
| Saturday night |
Partly cloudy. Patchy light fog in the evening, then moderate fog after midnight. Low 71°. Wind south-southwest around 5 mph, gusting to 15 mph. |
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