| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Friday, 05-Jun-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Partly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. A slight chance of rain. Scattered thundershowers possible. High 86°. UV index up to 6. Wind south around 9 mph, gusting to 28 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Tonight |
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Low 70°. Wind south-southwest around 7 mph, gusting to 22 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Mostly cloudy to cloudy. A slight chance of rain. Scattered thundershowers possible. Hot. High 87°. UV index up to 6. Wind south-southwest around 7 mph, gusting to 25 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday night |
Mostly cloudy to cloudy. A slight chance of rain. Precipitation showery or intermittent. Low 72°. Wind south-southwest around 4 mph, gusting to 22 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday |
Cloudy. Rain likely. Scattered thundershowers possible. High 80°. UV index up to 5. Wind south-southeast around 5 mph, gusting to 19 mph. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Sunday night |
Cloudy. Light to moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thunderstorms likely. Low 72°. Wind south-southeast around 6 mph, gusting to 17 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Monday |
Partly to mostly cloudy. Moderate fog. Rain likely in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. High 80°. UV index up to 9. Wind south-southeast around 6 mph, gusting to 18 mph, in the morning, becoming south-southwest in the afternoon. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Monday night |
Mostly cloudy. Moderate fog. Rain likely. Scattered thunderstorms likely. Low 73°. Wind south around 5 mph, gusting to 16 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Tuesday |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Precipitation showery or intermittent. Hot. High 89°. Heat index up to 99°. UV index up to 9. Wind south-southwest around 6 mph, gusting to 24 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 fair after midnight. Light to moderate fog in the evening, then moderate fog after midnight. Low 74°. Wind south-southwest around 5 mph, gusting to 20 mph. |
| Wednesday |
Partly to mostly cloudy in the morning, becoming sunny in the afternoon. Moderate fog in the morning. Hot. High 92°. Heat index up to 102°. UV index up to 9. Wind south-southwest around 6 mph, gusting to 23 mph, in the morning, becoming 9 mph, gusting to 26 mph, in the afternoon. |
| Wednesday night |
Clear in the evening, becoming mostly clear after midnight. Patchy light fog in the evening, then moderate fog after midnight. Low 73°. Wind south-southwest around 5 mph, gusting to 21 mph. |
| Thursday |
Mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Light to moderate fog in the morning. Very hot. High 94°. Heat index up to 104°. UV index up to 10. Wind south-southwest around 8 mph, gusting to 24 mph. |
| Thursday night |
Fair in the evening, becoming fair to partly cloudy after midnight. Moderate fog after midnight. Low 72°. Wind west-southwest around 4 mph, gusting to 17 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.