| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Wednesday, 22-Jul-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Partly to mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Relatively cool. Low 64°. Wind northeast around 5 mph, gusting to 23 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 82°. UV index up to 7. Wind northeast around 4 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday night |
Partly to mostly cloudy. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Relatively cool. Low 64°. Wind east-northeast around 4 mph, gusting to 19 mph. Chance of precipitation 50 percent. Precipitation mostly around a quarter of an inch. |
| Friday |
Dense overcast. Light to moderate fog in the morning. Rain likely in the morning, then a chance of rain in the afternoon. Relatively cool. High 75°. UV index up to 5. Wind east around 4 mph, gusting to 18 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Friday night |
Mostly cloudy to cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Precipitation showery or intermittent. Relatively cool. Low 66°. Wind east around 6 mph, gusting to 16 mph, in the evening, becoming southeast after midnight. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Saturday |
Partly to mostly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. High 89°. Heat index up to 94°. UV index up to 9. Wind southeast around 5 mph, gusting to 20 mph, in the morning, becoming west in the afternoon. Chance of precipitation 50 percent. Precipitation mostly around a quarter of an inch. |
| Saturday night |
Fair to partly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog after midnight. Low 72°. Wind northeast around 2 mph, gusting to 17 mph. |
| Sunday |
Partly cloudy. Patchy light fog in the morning. Hot. High 91°. Heat index up to 99°. UV index up to 7. Wind east-northeast around 3 mph, gusting to 19 mph. |
| Sunday night |
Clear in the evening, becoming fair after midnight. Patchy light fog after midnight. Low 72°. Wind east-southeast around 4 mph, gusting to 17 mph, in the evening, becoming south after midnight. |
| Monday |
Partly to mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Hot. High 95°. Heat index up to 105°. UV index up to 9. Wind south-southwest around 6 mph, gusting to 18 mph. |
| Monday night |
Clear in the evening, becoming fair after midnight. Patchy light fog after midnight. Low 74°. Wind southwest around 5 mph in the evening, becoming west-northwest after midnight. |
| Tuesday |
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. Very hot. High 97°. Heat index up to 104°. UV index up to 8. Wind west around 9 mph, gusting to 23 mph. |
| Tuesday night |
Partly to mostly cloudy in the evening, becoming clear after midnight. Low 73°. Wind west around 4 mph, gusting to 17 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.