| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Wednesday, 02-Sep-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair in the evening, becoming clear after midnight. Warm. Low 74°. Wind south-southwest around 4 mph, gusting to 22 mph. |
| Thursday |
Sunny in the morning, becoming mostly sunny in the afternoon. Extremely hot. High 99°. Heat index up to 105°. UV index up to 8. Wind south-southwest around 6 mph, gusting to 24 mph. |
| Thursday night |
Fair to partly cloudy in the evening, becoming fair after midnight. Warm. Low 73°. Wind south around 5 mph, gusting to 18 mph. |
| Friday |
Sunny. Extremely hot. High 98°. Heat index up to 106°. UV index up to 8. Wind southwest around 4 mph, gusting to 23 mph. |
| Friday night |
Mostly clear in the evening, becoming fair after midnight. Warm. Low 72°. Wind south-southwest around 2 mph. |
| Saturday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Very hot. High 97°. Heat index up to 104°. UV index up to 7. Wind southeast around 4 mph, gusting to 21 mph, in the morning, becoming north-northwest in the afternoon. |
| Saturday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. A chance of rain. Low 70°. Wind northeast around 3 mph, gusting to 15 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday |
Mostly sunny in the morning, becoming sunny in the afternoon. Patchy light fog in the morning. Hot. High 90°. Heat index up to 96°. UV index up to 8. Wind northeast around 3 mph, gusting to 18 mph, in the morning, becoming 6 mph, gusting to 22 mph, in the afternoon. |
| Sunday night |
Partly cloudy in the evening, becoming fair after midnight. Moderate fog after midnight. A slight chance of rain. Low 67°. Wind east-northeast around 6 mph, gusting to 18 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Sunny. Light to moderate fog in the morning. Hot. High 89°. Heat index up to 94°. UV index up to 7. Wind east around 5 mph, gusting to 22 mph. |
| Monday night |
Mostly clear in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Low 65°. Wind east-southeast around 5 mph, gusting to 16 mph. |
| Tuesday |
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Extremely hot. High 99°. Heat index up to 104°. UV index up to 7. Wind southwest around 7 mph, gusting to 20 mph, in the morning, becoming 10 mph, gusting to 24 mph, in the afternoon. |
| Tuesday night |
Partly cloudy in the evening, becoming clear after midnight. Low 71°. Wind southwest around 7 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.