| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 15-Sep-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. A slight chance of rain. Warm. Low 74°. Wind northeast around 4 mph, gusting to 22 mph, in the evening, becoming south after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Near record heat. High 99°. Heat index up to 106°. UV index up to 7. Wind south-southwest around 4 mph, gusting to 24 mph, in the morning, becoming west-southwest in the afternoon. |
| Wednesday night |
Partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Warm. Low 69°. Wind south around 4 mph, gusting to 17 mph. |
| Thursday |
Sunny. Near record heat. High 100°. Heat index up to 106°. UV index up to 7. Wind southwest around 5 mph, gusting to 24 mph, in the morning, becoming west-northwest in the afternoon. |
| Thursday night |
Fair to partly cloudy in the evening, becoming fair after midnight. A slight chance of rain. Low 68°. Wind north-northeast around 2 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Sunny in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 95°. Heat index up to 99°. UV index up to 7. Wind east-northeast around 3 mph, gusting to 20 mph. |
| Friday night |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 68°. Wind south-southeast around 4 mph. |
| Saturday |
Mostly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Very hot. High 96°. UV index up to 6. Wind southwest around 7 mph, gusting to 20 mph. |
| Saturday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 66°. Wind south around 2 mph in the evening, becoming west-southwest after midnight. |
| Sunday |
Sunny. Very hot. High 92°. UV index up to 7. Wind west around 3 mph, gusting to 18 mph, in the morning, becoming 8 mph, gusting to 22 mph, in the afternoon. |
| Sunday night |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Low 66°. Wind northwest around 3 mph. |
| Monday |
Partly to mostly cloudy in the morning, becoming sunny in the afternoon. Unusually hot. High 88°. UV index up to 6. Wind west-northwest around 4 mph, gusting to 24 mph, in the morning, becoming 9 mph, gusting to 25 mph, in the afternoon. |
| Monday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Low 60°. Wind northwest around 4 mph, gusting to 19 mph, in the evening, becoming northeast after midnight. |
WXSIM forecast formatting script by Saratoga-Weather.org.