| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
||||||||||||||||||||||||||||||||||||||||||||||||
| Updated: Sunday, 19-Jul-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
|
| Tonight |
Fair to partly cloudy in the evening, becoming partly cloudy after midnight. Light to moderate fog in the evening, then moderate fog after midnight. Rain likely. Low 76°. Wind east-northeast around 4 mph, gusting to 22 mph. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch. |
| Monday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. Rain likely. High 90°. Heat index up to 100°. UV index up to 7. Wind southeast around 3 mph, gusting to 17 mph, in the morning, becoming southwest in the afternoon. Chance of precipitation 60 percent. Precipitation mostly around a tenth of an inch. |
| Monday night |
Fair to partly cloudy in the evening, becoming fair after midnight. Patchy light fog in the evening, then moderate to dense fog after midnight. A chance of rain. Low 76°. Wind south-southwest around 4 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday |
Partly to mostly sunny in the morning, becoming partly to mostly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. Precipitation showery or intermittent. High 90°. Heat index up to 98°. UV index up to 8. Wind west-northwest around 7 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Fair to partly cloudy. Light to moderate fog after midnight. Low 70°. Wind north around 6 mph, gusting to 18 mph. |
| Wednesday |
Partly cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. High 87°. UV index up to 7. Wind north around 7 mph, gusting to 25 mph. |
| Wednesday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Relatively cool. Low 66°. Wind northeast around 5 mph, gusting to 24 mph. |
| Thursday |
Partly cloudy. High 88°. UV index up to 9. Wind east-northeast around 4 mph, gusting to 24 mph. |
| Thursday night |
Partly cloudy. Relatively cool. Low 66°. Wind east-northeast around 4 mph, gusting to 22 mph. |
| Friday |
Mostly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. A chance of rain. High 85°. UV index up to 6. Wind east around 5 mph, gusting to 24 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Friday night |
Partly to mostly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Relatively cool. Low 66°. Wind east around 4 mph, gusting to 22 mph. |
| Saturday |
Sunny. Patchy light fog in the morning. High 87°. UV index up to 9. Wind east around 7 mph, gusting to 29 mph, in the morning, becoming 10 mph, gusting to 29 mph, in the afternoon. |
| Saturday night |
Mostly clear. Relatively cool. Low 65°. Wind east around 4 mph, gusting to 25 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.