| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Wednesday, 01-Jul-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Clear. Patchy light fog in the evening, then moderate fog after midnight. Low 74°. Wind south around 5 mph, gusting to 21 mph. |
| Thursday |
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. Scattered thundershowers possible. Hot. High 94°. Heat index up to 104°. UV index up to 10. Wind south around 6 mph, gusting to 22 mph. Chance of precipitation 40 percent. Precipitation mostly around a tenth of an inch. |
| Thursday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. Moderate fog. A chance of rain. Low 75°. Wind south around 5 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch. |
| Friday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. A chance of rain. Scattered thundershowers possible. Hot. High 92°. Heat index up to 103°. UV index up to 9. Wind south around 5 mph, gusting to 21 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Scattered thundershowers possible. Low 74°. Wind south around 4 mph, gusting to 15 mph, in the evening, becoming southeast after midnight. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch. |
| Saturday |
Partly to mostly cloudy. Moderate fog. A slight chance of rain in the morning, then rain likely in the afternoon. Scattered thundershowers possible. High 89°. Heat index up to 97°. UV index up to 7. Wind south-southwest around 4 mph, gusting to 21 mph, in the morning, becoming west-southwest in the afternoon. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch. |
| Saturday night |
Fair to partly cloudy in the evening, becoming mostly clear after midnight. Moderate fog. Low 74°. Wind southwest around 2 mph. |
| Sunday |
Partly cloudy. Light to moderate fog in the morning. A chance of rain. High 90°. Heat index up to 100°. UV index up to 9. Wind west-northwest around 3 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday night |
Partly cloudy. Moderate fog. A chance of rain. Low 74°. Wind north-northeast around 4 mph, gusting to 18 mph. Chance of precipitation 50 percent. Precipitation mostly less than a quarter of an inch. |
| Monday |
Partly to mostly cloudy in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning. Rain likely. High 88°. Heat index up to 96°. UV index up to 9. Wind north-northeast around 4 mph, gusting to 21 mph. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch. |
| Monday night |
Moderate fog. Rain likely in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Low 74°. Wind east-southeast around 4 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch. |
| Tuesday |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. A chance of rain. High 87°. Heat index up to 95°. UV index up to 10. Wind west-southwest around 8 mph, gusting to 25 mph, in the morning, becoming 12 mph, gusting to 29 mph, in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Moderate fog. A slight chance of rain. Low 73°. Wind west-northwest around 7 mph, gusting to 25 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
WXSIM forecast formatting script by Saratoga-Weather.org.