| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 18-Aug-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Partly cloudy. A chance of rain. High 87°. UV index up to 8. Wind south around 3 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tonight |
Fair in the evening, becoming mostly cloudy after midnight. Light to moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Low 68°. Wind east-southeast around 3 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Wednesday |
Mostly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. Patchy light fog in the morning. Rain likely. Scattered thunderstorms likely. High 81°. UV index up to 5. Wind east around 4 mph, gusting to 17 mph. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch. |
| Wednesday night |
Partly cloudy in the evening, becoming fair after midnight. Moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thundershowers possible. Low 69°. Wind east 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. Light to moderate fog in the morning. High 85°. UV index up to 6. Wind northeast around 5 mph, gusting to 23 mph. |
| Thursday night |
Mostly clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 66°. Wind northeast around 2 mph, gusting to 18 mph, in the evening, becoming east after midnight. |
| Friday |
Sunny. Patchy light fog in the morning. High 86°. UV index up to 7. Wind south-southeast around 3 mph, gusting to 21 mph, in the morning, becoming west-northwest in the afternoon. |
| Friday night |
Mostly clear in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Low 69°. Wind east-northeast around 2 mph, gusting to 15 mph, in the evening, becoming west-southwest after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Mostly sunny. Light to moderate fog in the morning. Hot. High 88°. Heat index up to 92°. UV index up to 7. Wind west-northwest around 5 mph, gusting to 20 mph, in the morning, becoming 8 mph, gusting to 24 mph, in the afternoon. |
| Saturday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 64°. Wind north around 5 mph, gusting to 20 mph. |
| Sunday |
Partly cloudy. Patchy light fog in the morning. High 84°. UV index up to 8. Wind north-northeast around 4 mph, gusting to 23 mph. |
| Sunday night |
Clear in the evening, becoming fair after midnight. Patchy light fog after midnight. Relatively cool. Low 63°. Wind east around 4 mph, gusting to 20 mph. |
| Monday |
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. High 84°. UV index up to 6. Wind east around 6 mph, gusting to 20 mph, in the morning, becoming 9 mph, gusting to 25 mph, in the afternoon. |
| Monday night |
Partly cloudy in the evening, becoming fair after midnight. Patchy light fog after midnight. Low 64°. Wind east around 5 mph, gusting to 21 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.
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