| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Saturday, 08-Aug-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair in the evening, becoming fair to partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain after midnight. Low 75°. Wind east around 3 mph, gusting to 18 mph, in the evening, becoming south-southeast after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday |
Partly to mostly sunny. Moderate fog in the morning. A chance of rain. Scattered thundershowers possible. Hot. High 89°. Heat index up to 98°. UV index up to 8. Wind south-southeast around 7 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Sunday night |
Fair in the evening, becoming fair to partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 75°. Wind south around 7 mph, gusting to 17 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Partly to mostly sunny in the morning, becoming mostly sunny in the afternoon. Light to moderate fog in the morning. Very hot. High 97°. Heat index up to 108°. UV index up to 8. Wind southwest around 7 mph, gusting to 25 mph. |
| Monday night |
Mostly clear in the evening, becoming fair to partly cloudy after midnight. Low 76°. Wind south-southwest around 6 mph, gusting to 18 mph. |
| Tuesday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely. Very hot. High 98°. Heat index up to 108°. UV index up to 7. Wind south-southwest around 6 mph, gusting to 24 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Low 76°. Wind south-southeast around 5 mph, gusting to 17 mph, in the evening, becoming southwest after midnight. |
| Wednesday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. A chance of rain. Scattered thundershowers possible. Very hot. High 95°. Heat index up to 107°. UV index up to 7. Wind west around 4 mph, gusting to 21 mph, in the morning, becoming south-southwest in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday night |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 75°. Wind south-southeast around 3 mph, gusting to 19 mph, in the evening, becoming east-northeast after midnight. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch. |
| Thursday |
Mostly cloudy. Light to moderate fog in the morning. Rain likely in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely. High 87°. Heat index up to 94°. UV index up to 7. Wind east around 3 mph, gusting to 20 mph. Chance of precipitation 80 percent. Precipitation mostly around a quarter of an inch. |
| Thursday night |
Mostly cloudy. Light to moderate fog in the evening, then moderate fog after midnight. Rain very likely. Scattered thunderstorms likely. Low 75°. Wind east-northeast around 5 mph, gusting to 18 mph. Chance of precipitation 90 percent. Precipitation mostly around half an inch. |
| Friday |
Mostly sunny in the morning, becoming mostly cloudy to cloudy in the afternoon. Moderate fog in the morning. A slight chance of rain in the morning. High 83°. UV index up to 6. Wind east-northeast around 7 mph, gusting to 26 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Mostly cloudy in the evening, becoming clear after midnight. Light to moderate fog after midnight. Low 68°. Wind east around 5 mph, gusting to 23 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.
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