| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Friday, 05-Jun-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Partly to mostly cloudy in the evening, becoming mostly cloudy after midnight. Light to moderate fog after midnight. Rain likely. Scattered thunderstorms likely. Low 72°. Wind south-southwest around 7 mph, gusting to 24 mph. Chance of precipitation 60 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Mostly cloudy to cloudy. Patchy light fog in the morning. A chance of rain. Thunderstorms very likely, some possibly severe. High 85°. UV index up to 6. Wind south-southwest around 7 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday night |
Cloudy. Patchy light fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 72°. Wind south-southwest around 3 mph, gusting to 19 mph, in the evening, becoming southeast after midnight. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday |
Mostly cloudy to cloudy. Patchy light fog in the morning. Rain likely. Thunderstorms very likely, some possibly severe. High 84°. UV index up to 7. Wind southeast around 7 mph, gusting to 24 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch. |
| Sunday night |
Mostly cloudy to cloudy. Light to moderate fog in the evening, then moderate fog after midnight. Rain likely. Thunderstorms very likely, some possibly severe. Low 72°. Wind south-southeast around 7 mph, gusting to 21 mph. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch. |
| Monday |
Cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning, then patchy light fog in the afternoon. Rain likely. Thunderstorms very likely, some possibly severe. High 86°. Heat index up to 93°. UV index up to 8. Wind south-southwest around 7 mph, gusting to 24 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch. |
| Monday night |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Moderate fog. Rain. Thunderstorms very likely, some possibly severe. Low 73°. Wind south-southwest around 4 mph, gusting to 21 mph. Chance of precipitation near 100 percent. Precipitation mostly between half an inch and one inch. |
| Tuesday |
Mostly cloudy to cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. Rain likely. Thunderstorms very likely, some possibly severe. Hot. High 89°. Heat index up to 99°. UV index up to 9. Wind south-southwest around 7 mph, gusting to 22 mph. Chance of precipitation 60 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Fair in the evening, becoming mostly clear after midnight. Moderate fog in the evening, then moderate to dense fog after midnight. Low 74°. Wind south-southwest around 5 mph, gusting to 17 mph. |
| Wednesday |
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Moderate fog in the morning. Very hot. High 93°. Heat index up to 104°. UV index up to 9. Wind south-southwest around 9 mph, gusting to 27 mph. |
| Wednesday night |
Clear. Moderate fog after midnight. Low 74°. Wind south-southwest around 7 mph, gusting to 21 mph. |
| Thursday |
Sunny. Moderate fog in the morning. Very hot. High 94°. Heat index up to 104°. UV index up to 10. Wind southwest around 8 mph, gusting to 25 mph. |
| Thursday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Light to moderate fog after midnight. A chance of rain after midnight. Scattered thundershowers possible. Low 73°. Wind southwest around 3 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
WXSIM forecast formatting script by Saratoga-Weather.org.