| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Friday, 04-Sep-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Clear in the evening, becoming fair to partly cloudy after midnight. Warm. Low 76°. Wind south-southwest around 3 mph, gusting to 19 mph. |
| Saturday |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Very hot. High 97°. Heat index up to 107°. UV index up to 8. Wind west-northwest around 4 mph, gusting to 22 mph, in the morning, becoming north-northwest in the afternoon. |
| Saturday night |
Fair to partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 71°. Wind northeast around 4 mph, gusting to 16 mph. |
| Sunday |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 90°. Heat index up to 94°. UV index up to 8. Wind northeast around 6 mph, gusting to 24 mph. |
| Sunday night |
Partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 65°. Wind northeast around 6 mph, gusting to 21 mph, in the evening, becoming east after midnight. |
| Monday |
Sunny. Patchy light fog in the morning. Hot. High 89°. UV index up to 8. Wind east around 5 mph, gusting to 24 mph. |
| Monday night |
Mostly clear in the evening, becoming fair to partly cloudy after midnight. Low 63°. Wind east around 4 mph, gusting to 18 mph. |
| Tuesday |
Sunny. Patchy light fog in the morning. Very hot. High 92°. UV index up to 7. Wind southeast around 4 mph, gusting to 23 mph. |
| Tuesday night |
Clear in the evening, becoming fair to partly cloudy after midnight. Low 68°. Wind southeast around 6 mph, gusting to 15 mph, in the evening, becoming south after midnight. |
| Wednesday |
Sunny in the morning, becoming mostly sunny in the afternoon. Very hot. High 95°. Heat index up to 99°. UV index up to 7. Wind west-southwest around 6 mph, gusting to 21 mph. |
| Wednesday night |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Light to moderate fog after midnight. A slight chance of rain in the evening, then rain likely after midnight. Low 66°. Wind north around 3 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Thursday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain. Hot. High 87°. UV index up to 6. Wind north-northeast around 4 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a quarter of an inch. |
| Thursday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Low 63°. Wind east-northeast around 5 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.