| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Sunday, 07-Jun-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Mostly cloudy to cloudy in the evening, becoming cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Thunderstorms very likely, some severe. Low 72°. Wind south around 7 mph, gusting to 23 mph. Chance of precipitation 70 percent. Precipitation mostly less than a quarter of an inch. |
| Monday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Rain likely. Thunderstorms very likely, some possibly severe. High 86°. Heat index up to 93°. UV index up to 7. Wind south around 8 mph, gusting to 25 mph, in the morning, becoming southwest in the afternoon. Chance of precipitation 60 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Thunderstorms very likely, some possibly severe. Low 73°. Wind south-southwest around 5 mph, gusting to 22 mph. Chance of precipitation 80 percent. Precipitation mostly around a quarter of an inch. |
| Tuesday |
Partly to mostly sunny. Moderate fog in the morning. A chance of rain. Scattered thunderstorms likely, some possibly severe. Hot. High 91°. Heat index up to 100°. UV index up to 9. Wind southwest around 7 mph, gusting to 25 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Mostly clear in the evening, becoming clear after midnight. Patchy light fog in the evening, then moderate fog after midnight. Low 73°. Wind southwest around 6 mph, gusting to 21 mph. |
| Wednesday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. Hot. High 93°. Heat index up to 102°. UV index up to 7. Wind south around 10 mph, gusting to 27 mph. |
| Wednesday night |
Fair in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 74°. Wind south around 7 mph, gusting to 23 mph. |
| Thursday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain in the morning, then rain likely in the afternoon. Thunderstorms very likely, some severe. Hot. High 93°. Heat index up to 103°. UV index up to 9. Wind south-southwest around 10 mph, gusting to 29 mph. Chance of precipitation 70 percent. Precipitation mostly less than a quarter of an inch. |
| Thursday night |
Moderate fog in the evening, then moderate to dense fog after midnight. Rain likely in the evening, then a slight chance of rain after midnight. Thunderstorms very likely, some severe. Low 71°. Wind west around 5 mph, gusting to 16 mph. Chance of precipitation 80 percent. Precipitation mostly between a quarter and half an inch. |
| Friday |
Sunny. Light to moderate fog in the morning. Hot. High 88°. Heat index up to 94°. UV index up to 8. Wind north around 3 mph, gusting to 21 mph, in the morning, becoming east-northeast in the afternoon. |
| Friday night |
Fair in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain after midnight. Scattered thunderstorms likely. Low 70°. Wind east-northeast around 4 mph, gusting to 17 mph, in the evening, becoming south-southeast after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. Rain likely. Scattered thunderstorms likely. High 86°. Heat index up to 92°. UV index up to 8. Wind south-southeast around 5 mph, gusting to 24 mph. Chance of precipitation 60 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, some possibly severe. Low 73°. Wind east-southeast around 5 mph, gusting to 22 mph, in the evening, becoming south-southeast after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
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