| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Wednesday, 01-Jul-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Sunny. Very hot. High 100°. Heat index up to 108°. UV index up to 11. Wind south-southwest around 6 mph, gusting to 27 mph. |
| Tonight |
Mostly clear in the evening, becoming fair to partly cloudy after midnight. Low 75°. Wind south-southwest around 5 mph, gusting to 22 mph. |
| Thursday |
Sunny in the morning, becoming partly cloudy in the afternoon. A chance of rain in the afternoon. Thunderstorms very likely, some possibly severe. Very hot. High 99°. Heat index up to 109°. UV index up to 10. Wind south-southwest around 5 mph, gusting to 25 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Thursday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Moderate fog. A chance of rain. Scattered thundershowers possible. Low 77°. Wind south-southeast around 4 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Friday |
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Moderate fog in the morning. Hot. High 95°. Heat index up to 107°. UV index up to 7. Wind south-southeast around 5 mph, gusting to 23 mph. |
| Friday night |
Partly to mostly cloudy. Patchy light fog after midnight. A chance of rain. Scattered thunderstorms likely, some possibly severe. Low 76°. Wind south around 4 mph, gusting to 16 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely, some possibly severe. Hot. High 93°. Heat index up to 104°. UV index up to 9. Wind southeast around 5 mph, gusting to 23 mph, in the morning, becoming south-southwest in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday night |
Partly to mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Thunderstorms very likely, some possibly severe. Low 76°. Wind south-southeast around 4 mph, gusting to 17 mph, in the evening, becoming west after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. Hot. High 94°. Heat index up to 105°. UV index up to 9. Wind west around 4 mph, gusting to 22 mph, in the morning, becoming north-northwest in the afternoon. |
| Sunday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain. Thunderstorms very likely, some possibly severe. Low 75°. Wind east-northeast around 4 mph, gusting to 17 mph, in the evening, becoming southwest near calm after midnight. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Monday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thunderstorms likely, some possibly severe. Hot. High 92°. Heat index up to 102°. UV index up to 9. Wind east around 2 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Mostly cloudy to cloudy in the evening, becoming partly to mostly cloudy after midnight. Light to moderate fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Thunderstorms very likely, some possibly severe. Low 76°. Wind south-southeast around 4 mph in the evening, becoming southwest after midnight. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Tuesday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. A chance of rain. Scattered thunderstorms likely. Hot. High 91°. Heat index up to 102°. UV index up to 8. Wind west around 4 mph, gusting to 22 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Fair to partly cloudy in the evening, becoming clear after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. Low 74°. Wind north-northwest around 2 mph, gusting to 18 mph, in the evening, becoming east after midnight. |
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