WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Wednesday, 27-May-2026 04:00 pm
 
Tonight

Partly Cloudy
Partly Cloudy
Thursday

Partly Cloudy
Partly Cloudy
Thursday
night
Mostly Cloudy
Mostly Cloudy
Friday

Rain likely
Rain likely
Friday
night
Chance rain
Chance rain
Saturday

Chance rain
Chance rain
Saturday
night
Mostly Cloudy
Mostly Cloudy
Sunday

Partly Cloudy
Partly Cloudy
.35 in. .1 in. .1 in.
Low: 64° High: 85° Low: 62° High: 77° Low: 65° High: 77° Low: 64° High: 85°
               
ENE
2-22
mph
ENE
5-23→9-26
mph
ENE
6-23
mph
E
5-19
mph
ENE
4
mph
ENE
5-21
mph
E
5-21
mph
ESE
6-25
mph
UV: 9
 Very High 
UV: 5
 Medium 
UV: 6
 High 
UV: 8
 Very High 

 

Tonight
 
Partly cloudy. Low 64°. Wind east-northeast around 2 mph, gusting to 22 mph.
Thursday
 
Partly cloudy. Hot. High 85°. UV index up to 9. Wind east-northeast around 5 mph, gusting to 23 mph, in the morning, becoming 9 mph, gusting to 26 mph, in the afternoon.
Thursday night
 
Partly to mostly cloudy. Low 62°. Wind east-northeast around 6 mph, gusting to 23 mph.
Friday
 
Mostly cloudy in the morning, becoming cloudy in the afternoon. A slight chance of rain in the morning, then rain likely in the afternoon. High 77°. UV index up to 5. Wind east around 5 mph, gusting to 19 mph. Chance of precipitation 60 percent. Precipitation mostly between a quarter and half an inch.
Friday night
 
Cloudy. Patchy light fog. A slight chance of rain in the evening, then a chance of rain after midnight. Precipitation showery or intermittent. Low 65°. Wind east-northeast around 4 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Saturday
 
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. Precipitation showery or intermittent. High 77°. UV index up to 6. Wind east-northeast around 5 mph, gusting to 21 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Saturday night
 
Mostly cloudy. Low 64°. Wind east around 5 mph, gusting to 21 mph.
Sunday
 
Partly cloudy. High 85°. UV index up to 8. Wind east-southeast around 6 mph, gusting to 25 mph.
Sunday night
 
Partly cloudy in the evening, becoming fair to partly cloudy after midnight. A slight chance of rain after midnight. Low 61°. Wind east-southeast around 3 mph, gusting to 21 mph. Chance of precipitation 20 percent. Precipitation mostly less than a tenth of an inch.
Monday
 
Partly to mostly sunny. Warm. High 85°. UV index up to 9. Wind northeast around 4 mph, gusting to 23 mph.
Monday night
 
Mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Low 61°. Wind east-northeast around 5 mph, gusting to 21 mph.
Tuesday
 
Partly cloudy in the morning, becoming mostly cloudy in the afternoon. High 81°. UV index up to 7. Wind east around 6 mph, gusting to 25 mph.
Tuesday night
 
Fair in the evening, becoming fair to partly cloudy after midnight. Relatively cool. Low 57°. Wind east-southeast around 4 mph, gusting to 21 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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