| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Thursday, 23-Jul-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Partly to mostly sunny in the morning, becoming mostly cloudy in the afternoon. A chance of rain. High 82°. UV index up to 7. Wind east-northeast around 3 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tonight |
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. Relatively cool. Low 64°. Wind east-northeast around 4 mph, gusting to 19 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Friday |
Cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog in the morning. A chance of rain. Relatively cool. High 77°. UV index up to 5. Wind southeast around 4 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Friday night |
Mostly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog in the evening, then moderate fog after midnight. Rain likely. Relatively cool. Low 67°. Wind southeast around 6 mph, gusting to 17 mph. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch. |
| Saturday |
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. High 87°. Heat index up to 93°. UV index up to 9. Wind south-southwest around 4 mph, gusting to 17 mph, in the morning, becoming west in the afternoon. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
| Saturday night |
Fair to partly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog after midnight. Low 73°. Wind northeast around 3 mph. |
| Sunday |
Partly cloudy. Hot. High 93°. Heat index up to 102°. UV index up to 7. Wind east-southeast around 3 mph, gusting to 20 mph. |
| Sunday night |
Mostly clear in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 73°. Wind south-southeast around 4 mph, gusting to 15 mph. |
| Monday |
Mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Very hot. High 97°. Heat index up to 107°. UV index up to 10. Wind south-southwest around 8 mph, gusting to 22 mph. |
| Monday night |
Clear. Low 74°. Wind southwest around 5 mph in the evening, becoming west after midnight. |
| Tuesday |
Sunny in the morning, becoming partly to mostly cloudy in the afternoon. Hot. High 96°. Heat index up to 104°. UV index up to 9. Wind west-northwest around 4 mph, gusting to 22 mph, in the morning, becoming north-northwest in the afternoon. |
| Tuesday night |
Partly cloudy in the evening, becoming clear after midnight. Patchy light fog after midnight. Low 70°. Wind east-northeast around 3 mph, gusting to 16 mph. |
| Wednesday |
Sunny. Patchy light fog in the morning. Hot. High 90°. Heat index up to 97°. UV index up to 9. Wind east-southeast around 5 mph, gusting to 23 mph. |
| Wednesday night |
Clear. Light to moderate fog after midnight. Low 71°. Wind east-southeast around 6 mph, gusting to 22 mph. |
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