| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 21-Jul-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair. Patchy light fog after midnight. A slight chance of rain after midnight. Relatively cool. Low 67°. Wind north around 7 mph, gusting to 25 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. High 84°. UV index up to 8. Wind north around 5 mph, gusting to 24 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Relatively cool. Low 63°. Wind northeast around 5 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday |
Partly cloudy. Patchy light fog in the morning. A chance of rain. High 83°. UV index up to 8. Wind east around 4 mph, gusting to 25 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. A chance of rain after midnight. Relatively cool. Low 64°. Wind east-northeast around 4 mph, gusting to 21 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Mostly cloudy to cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog. Rain likely. Precipitation showery or intermittent. Unusually cool. High 73°. UV index up to 4. Wind east-southeast around 3 mph, gusting to 15 mph. Chance of precipitation 80 percent. Precipitation mostly around an inch. |
| Friday night |
Cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Light to moderate fog. Rain likely in the evening, then a chance of rain after midnight. Precipitation showery or intermittent. Relatively cool. Low 68°. Wind east-southeast around 5 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Saturday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. Rain likely in the morning, then a slight chance of rain in the afternoon. Precipitation showery or intermittent. High 87°. Heat index up to 92°. UV index up to 8. Wind south-southeast around 4 mph, gusting to 21 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Saturday night |
Fair in the evening, becoming mostly cloudy after midnight. Patchy light fog after midnight. Low 71°. Wind south-southeast around 2 mph, gusting to 19 mph. |
| Sunday |
Sunny. Patchy light fog in the morning. Hot. High 93°. Heat index up to 102°. UV index up to 9. Wind south-southeast around 4 mph, gusting to 21 mph. |
| Sunday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 73°. Wind south-southwest around 5 mph, gusting to 17 mph. |
| Monday |
Mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Breezy and very hot. High 97°. Heat index up to 105°. UV index up to 9. Wind southwest around 10 mph, gusting to 25 mph, in the morning, becoming 14 mph, gusting to 27 mph, in the afternoon. |
| Monday night |
Clear in the evening, becoming mostly clear after midnight. Low 71°. Wind west-southwest around 7 mph, gusting to 21 mph, in the evening, becoming north after midnight. |
WXSIM forecast formatting script by Saratoga-Weather.org.
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