| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Sunday, 02-Aug-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair to partly cloudy. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain. Low 67°. Wind northeast around 3 mph, gusting to 23 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Partly to mostly sunny. Light to moderate fog in the morning. A chance of rain. High 84°. UV index up to 8. Wind northeast around 3 mph, gusting to 21 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Fair. Light to moderate fog after midnight. Relatively cool. Low 66°. Wind east-southeast around 3 mph, gusting to 15 mph. |
| Tuesday |
Mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. High 88°. Heat index up to 92°. UV index up to 8. Wind southeast around 4 mph, gusting to 22 mph. |
| Tuesday night |
Mostly clear in the evening, becoming clear after midnight. Patchy light fog after midnight. Relatively cool. Low 66°. Wind southeast around 5 mph, gusting to 18 mph. |
| Wednesday |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 92°. Heat index up to 96°. UV index up to 9. Wind south around 5 mph, gusting to 23 mph. |
| Wednesday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Precipitation showery or intermittent. Low 70°. Wind east around 5 mph, gusting to 17 mph, in the evening, becoming south-southwest after midnight. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Thursday |
Mostly cloudy. Light to moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. High 88°. Heat index up to 94°. UV index up to 6. Wind southwest around 4 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Thursday night |
Partly to mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Light to moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thundershowers possible. Low 72°. Wind east-northeast around 2 mph, gusting to 16 mph, in the evening, becoming south-southeast after midnight. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
| Friday |
Mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain. High 88°. Heat index up to 94°. UV index up to 8. Wind west around 3 mph, gusting to 23 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog after midnight. Low 72°. Wind east-southeast around 3 mph, gusting to 18 mph. |
| Saturday |
Partly cloudy in the morning, becoming mostly cloudy in the afternoon. Light to moderate fog in the morning. A slight chance of rain in the afternoon. Scattered thunderstorms likely. Hot. High 92°. Heat index up to 99°. UV index up to 6. Wind southwest around 5 mph, gusting to 18 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday night |
Partly cloudy in the evening, becoming clear after midnight. Patchy light fog in the evening, then moderate fog after midnight. Low 72°. Wind southeast around 8 mph, gusting to 16 mph, in the evening, becoming south-southwest around 5 mph after midnight. |
WXSIM forecast formatting script by Saratoga-Weather.org.