| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Friday, 14-Aug-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Patchy light fog. A chance of rain in the evening, then a slight chance of rain after midnight. Scattered thundershowers possible. Warm. Low 76°. Wind south around 4 mph, gusting to 19 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Rain likely. Precipitation showery or intermittent. Hot. High 92°. Heat index up to 104°. UV index up to 8. Wind southwest around 6 mph, gusting to 19 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
| Saturday night |
Partly cloudy. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain. Scattered thundershowers possible. Low 76°. Wind north-northwest around 2 mph in the evening, becoming west after midnight. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday |
Partly to mostly cloudy. Moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. Hot. High 92°. Heat index up to 104°. UV index up to 7. Wind west-northwest around 4 mph, gusting to 18 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Moderate fog. Rain likely in the evening, then a slight chance of rain after midnight. Scattered thundershowers possible. Low 73°. Wind north around 4 mph, gusting to 18 mph. Chance of precipitation 80 percent. Precipitation mostly around half an inch. |
| Monday |
Partly cloudy. Moderate fog in the morning. A slight chance of rain in the morning. High 86°. UV index up to 6. Wind north around 5 mph, gusting to 22 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Partly cloudy in the evening, becoming mostly clear after midnight. Light to moderate fog after midnight. Low 68°. Wind north around 2 mph, gusting to 19 mph. |
| Tuesday |
Mostly sunny in the morning, becoming sunny in the afternoon. Light to moderate fog in the morning. Hot. High 88°. Heat index up to 94°. UV index up to 8. Wind east-southeast around 2 mph, gusting to 20 mph. |
| Tuesday night |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 72°. Wind southeast around 6 mph, gusting to 15 mph. |
| Wednesday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Hot. High 92°. Heat index up to 98°. UV index up to 8. Wind south around 7 mph, gusting to 22 mph, in the morning, becoming west-northwest in the afternoon. |
| Wednesday night |
Mostly cloudy. Patchy light fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Low 69°. Wind north around 5 mph, gusting to 19 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Thursday |
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. High 81°. UV index up to 7. Wind north around 8 mph, gusting to 28 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday night |
Mostly cloudy to cloudy in the evening, becoming cloudy after midnight. Patchy light fog after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Low 68°. Wind north around 5 mph, gusting to 23 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
WXSIM forecast formatting script by Saratoga-Weather.org.