WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Friday, 19-Jun-2026 04:00 pm
 
Tonight

Partly Cloudy
Partly Cloudy
Saturday

Partly Cloudy
Partly Cloudy
Saturday
night
Partly Cloudy
Partly Cloudy
Sunday

Thunder storm
Thunder storm
Sunday
night
Rain likely
Rain likely
Monday

Chance rain
Chance rain
Monday
night
Mostly Cloudy
Mostly Cloudy
Tuesday

Partly Cloudy
Partly Cloudy
<.1 in. .5 in. 1.0 in. <.1 in.
Low: 65° High: 89° Low: 66° High: 80° Low: 69° High: 78° Low: 65° High: 81°
               
E→S
2-23
mph
W→SSW
3-22
mph
E
5-19
mph
SE→S
8-21
mph
W
7-19
mph
NNW
7-25
mph
NE
4-23
mph
NE
4-23
mph
UV: 9
 Very High 
UV: 6
 High 
UV: 5
 Medium 
UV: 8
 Very High 

 

Tonight
 
Partly cloudy. Relatively cool. Low 65°. Wind east around 2 mph, gusting to 23 mph, in the evening, becoming south after midnight.
Saturday
 
Partly to mostly sunny in the morning, becoming partly cloudy in the afternoon. High 89°. UV index up to 9. Wind west around 3 mph, gusting to 22 mph, in the morning, becoming south-southwest in the afternoon.
Saturday night
 
Fair to partly cloudy in the evening, becoming mostly cloudy after midnight. A chance of rain. Low 66°. Wind east around 5 mph, gusting to 19 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Sunday
 
Dense overcast in the morning, becoming mostly cloudy to cloudy in the afternoon. Patchy light fog in the morning. Rain likely. Scattered thundershowers possible. High 80°. UV index up to 6. Wind southeast around 8 mph, gusting to 21 mph, in the morning, becoming south in the afternoon. Chance of precipitation 80 percent. Precipitation mostly around half an inch.
Sunday night
 
Partly cloudy in the evening, becoming cloudy after midnight. Moderate fog in the evening, then light to moderate fog after midnight. Rain likely in the evening, then a slight chance of rain after midnight. Precipitation showery or intermittent. Low 69°. Wind west around 7 mph, gusting to 19 mph. Chance of precipitation 80 percent. Precipitation mostly around 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. High 78°. UV index up to 5. Wind north-northwest around 7 mph, gusting to 25 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Monday night
 
Mostly cloudy to cloudy. Relatively cool. Low 65°. Wind northeast around 4 mph, gusting to 23 mph.
Tuesday
 
Mostly cloudy in the morning, becoming partly cloudy in the afternoon. High 81°. UV index up to 8. Wind northeast around 4 mph, gusting to 23 mph.
Tuesday night
 
Mostly clear. Patchy light fog after midnight. Relatively cool. Low 60°. Wind northeast around 2 mph, gusting to 18 mph.
Wednesday
 
Mostly sunny in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A slight chance of rain in the morning, then a chance of rain in the afternoon. High 82°. UV index up to 7. Wind west-southwest around 4 mph, gusting to 22 mph, in the morning, becoming northwest in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Wednesday night
 
Mostly cloudy in the evening, becoming fair to partly cloudy after midnight. Patchy light fog in the evening, then moderate fog after midnight. Rain likely. Precipitation showery or intermittent. Relatively cool. Low 64°. Wind north-northeast around 3 mph, gusting to 17 mph, in the evening, becoming south after midnight. Chance of precipitation 60 percent. Precipitation mostly around a quarter of an inch.
Thursday
 
Mostly cloudy to cloudy in the morning, becoming partly cloudy in the afternoon. Patchy light fog in the morning. A chance of rain. Precipitation showery or intermittent. High 82°. UV index up to 8. Wind west-southwest around 4 mph, gusting to 22 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Thursday night
 
Fair in the evening, becoming mostly cloudy after midnight. Patchy light fog after midnight. Low 67°. Wind north around 3 mph, gusting to 21 mph.

WXSIM forecast formatting script by Saratoga-Weather.org.

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