| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Monday, 27-Jul-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Mostly sunny. Extremely hot. High 103°. Heat index up to 113°. UV index up to 10. Wind west-southwest around 6 mph, gusting to 25 mph. |
| Tonight |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thunderstorms likely, some possibly severe. Warm. Low 79°. Wind west-southwest around 5 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tuesday |
Partly to mostly cloudy in the morning, becoming mostly cloudy in the afternoon. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. Hot. High 93°. Heat index up to 103°. UV index up to 7. Wind north-northwest around 5 mph, gusting to 23 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Tuesday night |
Fair to partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog in the evening, then moderate fog after midnight. A slight chance of rain. Low 72°. Wind northeast around 4 mph, gusting to 19 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Sunny. Light to moderate fog in the morning. Hot. High 90°. Heat index up to 96°. UV index up to 9. Wind east around 5 mph, gusting to 24 mph. |
| Wednesday night |
Clear. Patchy light fog after midnight. Low 68°. Wind east around 4 mph, gusting to 22 mph. |
| Thursday |
Mostly sunny. Patchy light fog in the morning. Hot. High 92°. Heat index up to 97°. UV index up to 9. Wind south-southeast around 5 mph, gusting to 24 mph. |
| Thursday night |
Partly cloudy. Patchy light fog after midnight. A slight chance of rain after midnight. Low 70°. Wind east around 4 mph, gusting to 21 mph, in the evening, becoming southeast after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
Partly cloudy in the morning, becoming cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. High 88°. Heat index up to 93°. UV index up to 5. Wind south-southeast around 7 mph, gusting to 25 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Friday night |
Mostly cloudy in the evening, becoming cloudy after midnight. Light to moderate fog. Rain very likely. Thunderstorms very likely, some possibly severe. Low 74°. Wind south-southeast around 7 mph, gusting to 19 mph. Chance of precipitation 80 percent. Precipitation mostly around an inch. |
| Saturday |
Cloudy in the morning, becoming mostly cloudy in the afternoon. Light to moderate fog in the morning, then patchy light fog in the afternoon. Rain likely. Thunderstorms very likely, some possibly severe. High 81°. UV index up to 5. Wind south-southeast around 5 mph, gusting to 21 mph, in the morning, becoming north-northeast in the afternoon. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch. |
| Saturday night |
Moderate to dense fog in the evening, then moderate fog after midnight. A chance of rain. Scattered thunderstorms likely. Low 71°. Wind northeast around 5 mph, gusting to 18 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Sunday |
Sunny. Moderate fog in the morning. High 85°. UV index up to 9. Wind north around 8 mph, gusting to 26 mph. |
| Sunday night |
Clear. Light to moderate fog after midnight. Low 68°. Wind east-northeast around 4 mph, gusting to 22 mph. |
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