| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Thursday, 17-Sep-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Near record heat. High 101°. Heat index up to 110°. UV index up to 6. Wind south-southwest around 5 mph, gusting to 26 mph, in the morning, becoming west in the afternoon. |
| Tonight |
Fair to partly cloudy in the evening, becoming clear after midnight. Warm. Low 72°. Wind west around 2 mph, gusting to 18 mph, in the evening, becoming north 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-northeast around 3 mph, gusting to 23 mph, in the morning, becoming east-southeast in the afternoon. |
| Friday night |
Fair in the evening, becoming clear after midnight. Warm. Low 70°. Wind southeast around 3 mph. |
| Saturday |
Sunny in the morning, becoming partly cloudy in the afternoon. Extremely hot. High 97°. Heat index up to 103°. UV index up to 7. Wind southwest around 5 mph, gusting to 24 mph. |
| Saturday night |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Warm. Low 69°. Wind south-southwest near calm in the evening, becoming west around 4 mph after midnight. |
| Sunday |
Partly to mostly cloudy. Very hot. High 92°. UV index up to 6. Wind west-northwest around 3 mph, gusting to 19 mph. |
| Sunday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Light to moderate fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Precipitation showery or intermittent. Low 64°. Wind north-northeast around 5 mph, gusting to 15 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Monday |
Partly cloudy. Moderate fog in the morning. A chance of rain. High 79°. UV index up to 6. Wind north-northeast around 4 mph, gusting to 18 mph, in the morning, becoming north-northwest in the afternoon. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Monday night |
Partly to mostly cloudy in the evening, becoming cloudy after midnight. Light to moderate fog. A chance of rain in the evening, then a slight chance of rain after midnight. Low 64°. Wind north-northwest around 6 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tuesday |
Cloudy. Patchy light fog in the morning. A slight chance of rain. High 72°. Wind north-northwest around 6 mph, gusting to 24 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Mostly cloudy to cloudy in the evening, becoming fair to partly cloudy after midnight. Light to moderate fog after midnight. Low 56°. Wind north around 5 mph, gusting to 21 mph. |
| Wednesday |
Sunny in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. High 77°. UV index up to 6. Wind north around 5 mph, gusting to 23 mph. |
| Wednesday night |
Partly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Low 58°. Wind north-northeast around 5 mph, gusting to 18 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.