| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Monday, 03-Aug-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Fair. Patchy light fog after midnight. Low 68°. Wind east around 4 mph, gusting to 21 mph, in the evening, becoming southeast after midnight. |
| Tuesday |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Hot. High 90°. Heat index up to 93°. UV index up to 8. Wind southeast around 4 mph, gusting to 22 mph. |
| Tuesday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. A slight chance of rain. Low 70°. Wind southeast around 5 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Partly cloudy. Light to moderate fog in the morning. A chance of rain. Precipitation showery or intermittent. High 89°. Heat index up to 94°. UV index up to 8. Wind south-southeast around 5 mph, gusting to 20 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday night |
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Moderate fog after midnight. A slight chance of rain in the evening, then rain likely after midnight. Precipitation showery or intermittent. Low 71°. Wind east around 4 mph, gusting to 16 mph. Chance of precipitation 70 percent. Precipitation mostly around half an inch. |
| Thursday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Moderate fog. Rain likely in the morning, then a chance of rain in the afternoon. Precipitation showery or intermittent. High 79°. UV index up to 5. Wind south-southeast around 5 mph. Chance of precipitation 70 percent. Precipitation mostly around an inch. |
| Thursday night |
Partly cloudy in the evening, becoming mostly cloudy after midnight. Patchy light fog. A slight chance of rain. Low 73°. Wind south-southeast around 3 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Friday |
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 88°. Heat index up to 95°. UV index up to 5. Wind southwest around 5 mph, gusting to 20 mph, in the morning, becoming west-northwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Fair to partly cloudy. Patchy light fog in the evening, then moderate fog after midnight. A slight chance of rain. Low 73°. Wind southeast around 3 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Saturday |
Mostly sunny. Moderate fog in the morning. Hot. High 91°. Heat index up to 99°. UV index up to 8. Wind south around 5 mph, gusting to 22 mph, in the morning, becoming west-southwest in the afternoon. |
| Saturday night |
Clear. Patchy light fog in the evening, then moderate fog after midnight. Low 73°. Wind south around 4 mph. |
| Sunday |
Mostly sunny in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. Hot. High 94°. Heat index up to 104°. UV index up to 8. Wind southwest around 9 mph, gusting to 21 mph. |
| Sunday night |
Mostly cloudy. A slight chance of rain. Scattered thundershowers possible. Low 75°. Wind south around 5 mph in the evening, becoming southeast after midnight. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
WXSIM forecast formatting script by Saratoga-Weather.org.
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