| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Saturday, 05-Sep-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair to partly cloudy in the evening, becoming clear after midnight. Warm. Low 74°. Wind east-northeast around 4 mph, gusting to 24 mph. |
| Sunday |
Partly to mostly sunny. Very hot. High 92°. Heat index up to 99°. UV index up to 7. Wind northeast around 6 mph, gusting to 26 mph. |
| Sunday night |
Fair to partly cloudy. Patchy light fog after midnight. Low 68°. Wind east-northeast around 6 mph, gusting to 21 mph. |
| Monday |
Sunny. Patchy light fog in the morning. Hot. High 89°. UV index up to 8. Wind east around 6 mph, gusting to 25 mph. |
| Monday night |
Fair in the evening, becoming clear after midnight. Patchy light fog after midnight. Low 63°. Wind east around 4 mph, gusting to 20 mph. |
| Tuesday |
Mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Very hot. High 94°. UV index up to 7. Wind south-southeast around 5 mph, gusting to 22 mph. |
| Tuesday night |
Fair in the evening, becoming fair to partly cloudy after midnight. Low 69°. Wind south-southeast around 6 mph, gusting to 17 mph. |
| Wednesday |
Mostly sunny in the morning, becoming partly cloudy in the afternoon. A chance of rain. Very hot. High 95°. Heat index up to 100°. UV index up to 6. Wind west-southwest around 6 mph, gusting to 20 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday night |
Partly to mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Light to moderate fog after midnight. A slight chance of rain in the evening, then rain likely after midnight. Precipitation showery or intermittent. Low 70°. Wind northeast around 3 mph in the evening, becoming north around 6 mph after midnight. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Thursday |
Cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. Rain likely in the morning, then a slight chance of rain in the afternoon. Precipitation showery or intermittent. Warm. High 84°. UV index up to 6. Wind north-northwest around 3 mph, gusting to 21 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Thursday night |
Fair to partly cloudy in the evening, becoming clear after midnight. Patchy light fog after midnight. Low 66°. Wind east near calm in the evening, becoming south-southeast after midnight. |
| Friday |
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Hot. High 85°. UV index up to 5. Wind south-southeast around 5 mph, gusting to 19 mph. |
| Friday night |
Mostly clear in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog after midnight. Low 66°. Wind southeast around 5 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.