| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Wednesday, 09-Sep-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Near record heat. High 103°. Heat index up to 109°. UV index up to 7. Wind west-southwest around 6 mph, gusting to 26 mph. |
| Tonight |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Warm. Low 75°. Wind south-southwest around 4 mph, gusting to 22 mph, in the evening, becoming west-northwest after midnight. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch. |
| Thursday |
Cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Hot. High 86°. Heat index up to 92°. UV index up to 5. Wind west around 3 mph, gusting to 23 mph, in the morning, becoming north in the afternoon. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Thursday night |
Partly to mostly cloudy in the evening, becoming fair after midnight. Patchy light fog after midnight. Warm. Low 70°. Wind north-northeast around 2 mph, gusting to 20 mph. |
| Friday |
Mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Hot. High 86°. UV index up to 6. Wind east around 5 mph, gusting to 24 mph. |
| Friday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 69°. Wind east-southeast around 4 mph, gusting to 18 mph, in the evening, becoming south-southeast after midnight. |
| Saturday |
Sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Very hot. High 91°. Heat index up to 97°. UV index up to 7. Wind south-southwest around 5 mph, gusting to 23 mph, in the morning, becoming west-southwest in the afternoon. |
| Saturday night |
Fair to partly cloudy in the evening, becoming fair after midnight. Patchy light fog after midnight. Low 69°. Wind east-northeast around 1 mph, gusting to 15 mph, in the evening, becoming south-southwest after midnight. |
| Sunday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Unusually hot. High 90°. Heat index up to 96°. UV index up to 6. Wind south-southwest around 2 mph, gusting to 17 mph, in the morning, becoming 5 mph, gusting to 21 mph, in the afternoon. |
| Sunday night |
Partly cloudy in the evening, becoming clear after midnight. Patchy light fog after midnight. Low 70°. Wind south-southeast around 6 mph. |
| Monday |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 93°. Heat index up to 102°. UV index up to 7. Wind south around 8 mph, gusting to 25 mph. |
| Monday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Warm. Low 73°. Wind south-southwest around 6 mph, gusting to 18 mph, in the evening, becoming west-southwest around 2 mph after midnight. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tuesday |
Partly to mostly cloudy. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Precipitation showery or intermittent. Hot. High 89°. Heat index up to 96°. UV index up to 4. Wind southwest around 3 mph, gusting to 20 mph, in the morning, becoming west-northwest around 6 mph, gusting to 22 mph, in the afternoon. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tuesday night |
Cloudy. Light to moderate fog in the evening, then patchy light fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Precipitation showery or intermittent. Warm. Low 73°. Wind east around 2 mph in the evening, becoming north-northwest after midnight. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
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