| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Monday, 20-Jul-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Partly to mostly sunny. A chance of rain. Hot. High 92°. Heat index up to 98°. UV index up to 9. Wind east-southeast around 3 mph, gusting to 21 mph, in the morning, becoming south-southeast in the afternoon. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tonight |
Partly cloudy. Moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 74°. Wind south-southeast around 4 mph in the evening, becoming southwest after midnight. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tuesday |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thunderstorms likely. High 90°. Heat index up to 98°. UV index up to 10. Wind west around 7 mph, gusting to 22 mph, in the morning, becoming north-northwest in the afternoon. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tuesday night |
Fair in the evening, becoming mostly clear after midnight. Light to moderate fog after midnight. Low 70°. Wind north-northwest around 6 mph, gusting to 19 mph. |
| Wednesday |
Sunny in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. High 85°. UV index up to 9. Wind north around 7 mph, gusting to 26 mph. |
| Wednesday night |
Partly cloudy in the evening, becoming fair after midnight. Relatively cool. Low 63°. Wind northeast around 5 mph, gusting to 25 mph. |
| Thursday |
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. High 84°. UV index up to 8. Wind northeast around 5 mph, gusting to 25 mph. |
| Thursday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. A slight chance of rain. Relatively cool. Low 63°. Wind northeast around 3 mph, gusting to 23 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. Patchy light fog in the afternoon. A chance of rain in the morning, then rain likely in the afternoon. Relatively cool. High 77°. UV index up to 5. Wind east-southeast around 3 mph, gusting to 19 mph, in the morning, becoming northeast in the afternoon. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Friday night |
Mostly cloudy to cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog. A chance of rain. Relatively cool. Low 68°. Wind east around 4 mph in the evening, becoming south-southeast after midnight. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Saturday |
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. High 88°. Heat index up to 93°. UV index up to 7. Wind south-southeast around 5 mph, gusting to 25 mph. |
| Saturday night |
Mostly cloudy in the evening, becoming partly cloudy after midnight. Moderate fog after midnight. Low 70°. Wind east-southeast around 4 mph, gusting to 21 mph. |
| Sunday |
Sunny. Moderate fog in the morning. Hot. High 92°. Heat index up to 100°. UV index up to 9. Wind south-southeast around 4 mph, gusting to 22 mph. |
| Sunday night |
Clear in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 73°. Wind southeast around 5 mph, gusting to 15 mph, in the evening, becoming south after midnight. |
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