| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Thursday, 23-Jul-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Relatively cool. Low 64°. Wind east-northeast around 3 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Friday |
Mostly cloudy to cloudy in the morning, becoming dense overcast in the afternoon. Patchy light fog in the morning. A chance of rain. Relatively cool. High 77°. UV index up to 4. Wind southeast around 3 mph, gusting to 17 mph. Chance of precipitation 50 percent. Precipitation mostly around a quarter of an inch. |
| Friday night |
Mostly cloudy. Patchy light fog in the evening, then light to moderate fog after midnight. Rain likely. Relatively cool. Low 67°. Wind southeast around 5 mph, gusting to 16 mph. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch. |
| Saturday |
Mostly cloudy in the morning, becoming partly 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. Precipitation showery or intermittent. High 87°. Heat index up to 92°. UV index up to 9. Wind south around 4 mph, gusting to 19 mph, in the morning, becoming west-northwest in the afternoon. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Saturday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog after midnight. Low 72°. Wind east-northeast around 3 mph, gusting to 16 mph, in the evening, becoming north after midnight. |
| Sunday |
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Hot. High 94°. Heat index up to 102°. UV index up to 9. Wind south-southwest around 3 mph, gusting to 21 mph. |
| Sunday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Low 73°. Wind south-southeast around 4 mph, gusting to 16 mph. |
| Monday |
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Hot. High 96°. Heat index up to 105°. UV index up to 9. Wind south-southeast around 7 mph, gusting to 21 mph, in the morning, becoming southwest in the afternoon. |
| Monday night |
Fair in the evening, becoming fair to partly cloudy after midnight. Low 75°. Wind south-southeast around 8 mph, gusting to 19 mph, in the evening, becoming west-southwest around 4 mph after midnight. |
| Tuesday |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Very hot. High 98°. Heat index up to 106°. UV index up to 9. Wind west-northwest around 4 mph, gusting to 23 mph, in the morning, becoming north-northwest in the afternoon. |
| Tuesday night |
Fair to partly cloudy. Low 72°. Wind north-northeast around 3 mph, gusting to 18 mph, in the evening, becoming east after midnight. |
| Wednesday |
Sunny. Hot. High 93°. Heat index up to 100°. UV index up to 9. Wind east around 4 mph, gusting to 17 mph, in the morning, becoming 7 mph, gusting to 19 mph, in the afternoon. |
| Wednesday night |
Mostly clear in the evening, becoming partly cloudy after midnight. Low 72°. Wind east-southeast around 4 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.
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