| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Thursday, 18-Jun-2026 04:00 pm | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Tonight |
Partly cloudy. Relatively cool. Low 60°. Wind west-northwest around 2 mph. |
| Friday |
Partly to mostly sunny in the morning, becoming mostly cloudy in the afternoon. High 81°. UV index up to 7. Wind north-northwest around 4 mph, gusting to 22 mph. |
| Friday night |
Partly cloudy. Relatively cool. Low 61°. Wind east-southeast around 3 mph in the evening, becoming south after midnight. |
| Saturday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. High 87°. UV index up to 8. Wind west around 3 mph, gusting to 22 mph, in the morning, becoming east in the afternoon. |
| Saturday night |
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Relatively cool. Low 64°. Wind east around 6 mph, gusting to 20 mph. |
| Sunday |
Dense overcast in the morning, becoming cloudy in the afternoon. Light to moderate fog in the afternoon. Rain very likely. Scattered thunderstorms likely. Relatively cool. High 74°. UV index up to 4. Wind south-southeast around 6 mph, gusting to 16 mph. Chance of precipitation 90 percent. Precipitation mostly between half an inch and one inch. |
| Sunday night |
Mostly cloudy in the evening, becoming cloudy after midnight. Moderate fog in the evening, then patchy light fog after midnight. Rain likely in the evening, then a chance of rain after midnight. Scattered thunderstorms likely. Low 69°, but temperatures rising after midnight. Wind southwest around 6 mph, gusting to 17 mph. Chance of precipitation 80 percent. Precipitation mostly around half an inch. |
| Monday |
Cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. Patchy light fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thunderstorms likely. High 79°. UV index up to 5. Wind north around 6 mph, gusting to 24 mph. Chance of precipitation 50 percent. Precipitation mostly less than a tenth of an inch. |
| Monday night |
Cloudy in the evening, becoming mostly cloudy to cloudy after midnight. A chance of rain in the evening, then a slight chance of rain after midnight. Low 66°. Wind north-northeast around 3 mph, gusting to 21 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday |
Partly to mostly cloudy in the morning, becoming mostly cloudy in the afternoon. A chance of rain. High 79°. UV index up to 6. Wind north-northeast around 6 mph, gusting to 23 mph, in the morning, becoming west-northwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog after midnight. Relatively cool. Low 64°. Wind north around 5 mph, gusting to 21 mph, in the evening, becoming south after midnight. |
| Wednesday |
Mostly sunny. Patchy light fog in the morning. High 78°. UV index up to 9. Wind west-northwest around 6 mph, gusting to 26 mph, in the morning, becoming 10 mph, gusting to 26 mph, in the afternoon. |
| Wednesday night |
Mostly clear in the evening, becoming mostly cloudy to cloudy after midnight. Relatively cool. Low 64°. Wind west-northwest around 3 mph, gusting to 22 mph. |
WXSIM forecast formatting script by Saratoga-Weather.org.