| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 30-Jun-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Sunny. Very hot. High 101°. Heat index up to 113°. UV index up to 10. Wind southwest around 7 mph, gusting to 28 mph. |
| Tonight |
Clear. Low 77°. Wind southwest around 5 mph, gusting to 24 mph. |
| Wednesday |
Sunny. Very hot. High 101°. Heat index up to 114°. UV index up to 11. Wind southwest around 7 mph, gusting to 27 mph. |
| Wednesday night |
Mostly clear. Patchy light fog after midnight. Low 76°. Wind south around 5 mph, gusting to 22 mph. |
| Thursday |
Partly cloudy. 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. Very hot. High 98°. Heat index up to 110°. UV index up to 11. Wind south around 6 mph, gusting to 25 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Thursday night |
Moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thundershowers possible. Low 78°. Wind south around 4 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Friday |
Partly cloudy. 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 95°. Heat index up to 110°. UV index up to 9. Wind south around 6 mph, gusting to 24 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Partly to mostly cloudy. Light to moderate 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 severe. Low 77°. Wind south-southwest around 4 mph, gusting to 17 mph. Chance of precipitation 80 percent. Precipitation mostly between half an inch and one inch. |
| Saturday |
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Moderate fog in the morning. Hot. High 92°. Heat index up to 104°. UV index up to 8. Wind west-southwest around 4 mph, gusting to 20 mph, in the morning, becoming south in the afternoon. |
| Saturday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. Rain likely. Thunderstorms very likely, some possibly severe. Low 76°. Wind south-southeast around 3 mph. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Sunday |
Mostly cloudy. Moderate fog in the morning, then patchy light fog in the afternoon. Rain likely. Thunderstorms very likely, some severe. High 86°. Heat index up to 96°. UV index up to 7. Wind south around 3 mph, gusting to 16 mph, in the morning, becoming northwest in the afternoon. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Sunday night |
Partly cloudy in the evening, becoming cloudy after midnight. Patchy light fog. A chance of rain. Thunderstorms very likely, some severe. Low 76°. Wind east-southeast around 2 mph in the evening, becoming south after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Partly cloudy. 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 92°. Heat index up to 102°. UV index up to 9. Wind east-southeast around 4 mph, gusting to 22 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Mostly cloudy in the evening, becoming cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. Rain likely. Severe thunderstorms likely, with possible tornados. Low 77°. Wind east-southeast around 3 mph, gusting to 16 mph, in the evening, becoming west-northwest after midnight. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
WXSIM forecast formatting script by Saratoga-Weather.org.