| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Monday, 14-Sep-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Clear. Patchy light fog after midnight. Low 66°. Wind southeast around 8 mph, gusting to 25 mph. |
| Tuesday |
Sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. Very hot. High 95°. UV index up to 7. Wind south around 7 mph, gusting to 23 mph, in the morning, becoming southwest in the afternoon. |
| Tuesday night |
Partly to mostly cloudy in the evening, becoming partly cloudy after midnight. A chance of rain. Precipitation showery or intermittent. Warm. Low 69°. Wind north-northeast around 3 mph in the evening, becoming south-southwest after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday |
Partly cloudy in the morning, becoming mostly sunny in the afternoon. A slight chance of rain. Very hot. High 94°. Heat index up to 100°. UV index up to 6. Wind south around 2 mph, gusting to 22 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Wednesday night |
Fair to partly cloudy in the evening, becoming clear after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A slight chance of rain. Warm. Low 69°. Wind south around 4 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Thursday |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 96°. Heat index up to 102°. UV index up to 7. Wind southwest around 4 mph, gusting to 21 mph, in the morning, becoming west-northwest in the afternoon. |
| Thursday night |
Fair in the evening, becoming partly cloudy after midnight. Patchy light fog after midnight. Warm. Low 69°. Wind east near calm. |
| Friday |
Sunny in the morning, becoming partly to mostly sunny in the afternoon. Patchy light fog in the morning. Very hot. High 94°. Heat index up to 100°. UV index up to 7. Wind east around 3 mph, gusting to 19 mph, in the morning, becoming southeast in the afternoon. |
| Friday night |
Fair to partly cloudy in the evening, becoming clear after midnight. Light to moderate fog after midnight. Low 69°. Wind southeast around 5 mph. |
| Saturday |
Sunny. Moderate fog in the morning. Very hot. High 93°. Heat index up to 100°. UV index up to 7. Wind south around 5 mph, gusting to 21 mph, in the morning, becoming west-southwest in the afternoon. |
| Saturday night |
Clear. Cool. Low 50°. Wind northwest around 3 mph. |
| Sunday |
Sunny. Warm. High 84°. UV index up to 6. Wind northwest around 6 mph, gusting to 15 mph. |
| Sunday night |
Clear. Cool. Low 52°. Wind northwest around 4 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.