| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Tuesday, 15-Sep-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Sunny in the morning, becoming partly cloudy in the afternoon. Near record heat. High 102°. Heat index up to 108°. UV index up to 6. Wind south-southwest around 7 mph, gusting to 26 mph. |
| Tonight |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. A slight chance of rain. Warm. Low 74°. Wind east around 2 mph in the evening, becoming south after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Partly to mostly sunny. Near record heat. High 100°. Heat index up to 107°. UV index up to 6. Wind southwest around 3 mph, gusting to 24 mph. |
| Wednesday night |
Fair to partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Warm. Low 71°. Wind south around 4 mph. |
| Thursday |
Sunny in the morning, becoming mostly sunny in the afternoon. Patchy light fog in the morning. Near record heat. High 100°. Heat index up to 107°. UV index up to 7. Wind southwest around 4 mph, gusting to 23 mph, in the morning, becoming west in the afternoon. |
| Thursday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Warm. Low 71°. Wind north-northeast near calm in the evening, becoming east-northeast after midnight. |
| Friday |
Sunny in the morning, becoming mostly sunny in the afternoon. Extremely hot. High 96°. Heat index up to 102°. UV index up to 7. Wind east around 3 mph, gusting to 20 mph, in the morning, becoming west-southwest in the afternoon. |
| Friday night |
Fair to partly cloudy in the evening, becoming fair after midnight. Low 68°. Wind east-southeast around 4 mph in the evening, becoming south after midnight. |
| Saturday |
Partly cloudy. Extremely hot. High 97°. Heat index up to 102°. UV index up to 6. Wind southwest around 6 mph, gusting to 22 mph. |
| Saturday night |
Fair in the evening, becoming fair to partly cloudy after midnight. Low 67°. Wind east-southeast around 3 mph in the evening, becoming west-southwest after midnight. |
| Sunday |
Partly to mostly sunny. Extremely hot. High 97°. Heat index up to 101°. UV index up to 7. Wind southwest around 3 mph, gusting to 21 mph. |
| Sunday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Low 67°. Wind north around 3 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Monday |
Cloudy. Patchy light fog in the morning. A chance of rain. Precipitation showery or intermittent. High 79°. Wind west around 4 mph, gusting to 20 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Monday night |
Fair to partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. Low 64°. Wind west-southwest around 3 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.