| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 01-Sep-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Clear. Low 71°. Wind south around 4 mph, gusting to 22 mph. |
| Wednesday |
Sunny. Very hot. High 98°. Heat index up to 104°. UV index up to 8. Wind southwest around 6 mph, gusting to 23 mph. |
| Wednesday night |
Fair in the evening, becoming clear after midnight. Low 71°. Wind south around 4 mph, gusting to 16 mph. |
| Thursday |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Very hot. High 98°. Heat index up to 105°. UV index up to 7. Wind southwest around 6 mph, gusting to 23 mph. |
| Thursday night |
Mostly clear in the evening, becoming clear after midnight. Low 72°. Wind south-southeast around 5 mph, gusting to 16 mph. |
| Friday |
Mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Very hot. High 98°. Heat index up to 105°. UV index up to 7. Wind southwest around 4 mph, gusting to 21 mph. |
| Friday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 72°. Wind south-southeast around 2 mph. |
| Saturday |
Partly to mostly sunny. A slight chance of rain. Very hot. High 92°. Heat index up to 101°. UV index up to 8. Wind north-northwest around 4 mph, gusting to 16 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday night |
Fair to partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 71°. Wind east around 2 mph in the evening, becoming southeast after midnight. |
| Sunday |
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the afternoon. Hot. High 92°. Heat index up to 98°. UV index up to 6. Wind west-northwest around 3 mph, gusting to 18 mph, in the morning, becoming north in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog. A slight chance of rain. Low 70°. Wind east around 3 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Partly to mostly cloudy in the morning, becoming cloudy in the afternoon. Patchy light fog in the morning. Hot. High 86°. UV index up to 5. Wind southwest around 5 mph, gusting to 15 mph, in the morning, becoming west-northwest in the afternoon. |
| Monday night |
Cloudy. Patchy light fog after midnight. A chance of rain. Low 72°. Wind east around 4 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
WXSIM forecast formatting script by Saratoga-Weather.org.