| WXSIM Forecast for:
O'Fallon Issued by: OFallonweather.com |
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| Updated: Saturday, 06-Jun-2026 05:00 am | ||||||||||||||||||||||||||||||||||||||||||||||||
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| Today |
Mostly cloudy in the morning, becoming mostly cloudy to cloudy in the afternoon. A chance of rain. Scattered thunderstorms likely, some possibly severe. Hot. High 88°. Heat index up to 93°. UV index up to 6. Wind southwest around 6 mph, gusting to 25 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Tonight |
Cloudy. A chance of rain. Scattered thunderstorms likely. Low 74°. Wind southwest around 5 mph, gusting to 23 mph, in the evening, becoming 2 mph after midnight. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday |
Mostly cloudy to cloudy in the morning, becoming mostly cloudy in the afternoon. A slight chance of rain in the morning, then a chance of rain in the afternoon. Thunderstorms very likely, some possibly severe. Hot. High 87°. Heat index up to 93°. UV index up to 7. Wind south-southeast around 5 mph, gusting to 24 mph, in the morning, becoming 9 mph, gusting to 26 mph, in the afternoon. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch. |
| Sunday night |
Cloudy. Patchy light fog in the evening, then light to moderate fog after midnight. Rain likely. Thunderstorms very likely, some possibly severe. Low 73°. Wind south-southeast around 6 mph, gusting to 22 mph. Chance of precipitation 60 percent. Precipitation mostly less than a quarter of an inch. |
| Monday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Moderate fog. Rain likely. Scattered thunderstorms likely. High 80°. UV index up to 5. Wind south around 5 mph, gusting to 18 mph. Chance of precipitation 80 percent. Precipitation mostly around an inch. |
| Monday night |
Moderate fog. A chance of rain in the evening, then rain likely after midnight. Scattered thunderstorms likely. Low 72°. Wind south-southwest around 4 mph. Chance of precipitation 70 percent. Precipitation mostly around an inch. |
| Tuesday |
Partly cloudy in the morning, becoming partly to mostly sunny in the afternoon. Moderate fog in the morning. A slight chance of rain. Scattered thunderstorms likely. Hot. High 90°. Heat index up to 100°. UV index up to 10. Wind southwest around 6 mph, gusting to 24 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch. |
| Tuesday night |
Partly cloudy in the evening, becoming mostly clear after midnight. Moderate to dense fog after midnight. Low 73°. Wind south around 6 mph, gusting to 21 mph. |
| Wednesday |
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. Moderate to dense fog in the morning. Hot. High 91°. Heat index up to 101°. UV index up to 9. Wind south around 8 mph, gusting to 26 mph. |
| Wednesday night |
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. Moderate fog after midnight. Low 73°. Wind south around 8 mph, gusting to 22 mph. |
| Thursday |
Mostly cloudy to cloudy. Patchy light fog in the morning, then light to moderate fog in the afternoon. A slight chance of rain in the morning, then rain likely in the afternoon. Thunderstorms very likely, some severe. High 86°. Heat index up to 93°. UV index up to 6. Wind south-southwest around 10 mph, gusting to 24 mph. Chance of precipitation 80 percent. Precipitation mostly around half an inch. |
| Thursday night |
Moderate fog. A chance of rain in the evening, then rain likely after midnight. Thunderstorms very likely, some possibly severe. Low 74°. Wind south-southwest around 6 mph, gusting to 18 mph. Chance of precipitation 80 percent. Precipitation mostly around half an inch. |
| Friday |
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. Moderate fog in the morning, then light to moderate fog in the afternoon. Rain likely in the morning, then a slight chance of rain in the afternoon. Thunderstorms very likely, some possibly severe. High 83°. UV index up to 8. Wind east around 4 mph, gusting to 20 mph. Chance of precipitation 70 percent. Precipitation mostly around an inch. |
| Friday night |
Partly to mostly cloudy in the evening, becoming dense overcast after midnight. Light to moderate fog. Rain likely. Thunderstorms very likely, some severe. Warm. Low 76°. Wind east-southeast around 5 mph, gusting to 19 mph, in the evening, becoming northwest after midnight. Chance of precipitation 80 percent. Precipitation mostly around an inch. |
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