WXSIM Forecast for: O'Fallon
Issued by: OFallonweather.com
Updated: Sunday, 01-Mar-2026 04:00 pm
 
Tonight

Chance rain
Chance rain
Monday

Mostly Cloudy
Mostly Cloudy
Monday
night
Overcast
Overcast
Tuesday

Rain likely
Rain likely
Tuesday
night
Rain likely
Rain likely
Wednesday

Rain likely
Rain likely
Wednesday
night
Rain likely
Rain likely
Thursday

Rain likely
Rain likely
.25 in.
.25 in.
<.1 in. .35 in. .25 in. .5 in. .5 in. .35 in.
Low: 28° High: 46° Low: 38° High: 52° Low: 43° High: 54° Low: 51° High: 67°
               
NE
7-25
mph
E
7-18
mph
E
5-16
mph
ESE
3
mph
NE
5
mph
NE→SE
2
mph
S
3→6
mph
SW
5-22
mph
UV: 5
 Medium 

 

Tonight
 
Cloudy in the evening, becoming dense overcast after midnight. A chance of a mix of rain, sleet, and snow in the evening, then a chance of a mix of sleet, snow, and rain after midnight. Low 28°. Wind northeast around 7 mph, gusting to 25 mph. Chance of precipitation 60 percent. Precipitation (liquid equivalent) mostly around a quarter of an inch. Snow or ice (on ground) accumulation about a quarter inch.
Monday
 
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. High 46°. Wind east around 7 mph, gusting to 18 mph.
Monday night
 
Dense overcast. A slight chance of rain in the evening, then a chance of rain after midnight. Low 38°. Wind east around 5 mph, gusting to 16 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Tuesday
 
Dense overcast. Patchy light fog in the morning. Rain likely in the morning, then a chance of rain in the afternoon. High 52°. Wind east-southeast around 3 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Tuesday night
 
Cloudy. Light to moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Low 43°. Wind northeast around 5 mph. Chance of precipitation 70 percent. Precipitation mostly around a quarter of an inch.
Wednesday
 
Dense overcast. Patchy light fog in the morning. Rain likely in the morning, then a chance of rain in the afternoon. High 54°. Wind northeast around 2 mph in the morning, becoming southeast in the afternoon. Chance of precipitation 80 percent. Precipitation mostly around half an inch.
Wednesday night
 
Dense overcast in the evening, becoming cloudy after midnight. Patchy light fog in the evening, then light to moderate fog after midnight. A chance of rain in the evening, then rain likely after midnight. Relatively mild. Low 51°, but temperatures rising after midnight. Wind south around 3 mph in the evening, becoming 6 mph after midnight. Chance of precipitation 70 percent. Precipitation mostly around half an inch.
Thursday
 
Mostly cloudy to cloudy in the morning, becoming partly to mostly cloudy in the afternoon. Light to moderate fog in the morning. Rain likely in the morning, then a slight chance of rain in the afternoon. Mild. High 67°. UV index up to 5. Wind southwest around 5 mph, gusting to 22 mph. Chance of precipitation 70 percent. Precipitation mostly between a quarter and half an inch.
Thursday night
 
Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. Patchy light fog after midnight. A chance of rain after midnight. Relatively mild. Low 52°. Wind southeast around 2 mph. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Friday
 
Mostly cloudy to cloudy in the morning, becoming partly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain. Exceptionally hot. High 78°. UV index up to 5. Wind south-southeast around 8 mph, gusting to 17 mph, in the morning, becoming 12 mph, gusting to 25 mph, in the afternoon. Chance of precipitation 30 percent. Precipitation mostly less than a tenth of an inch.
Friday night
 
Mostly cloudy to cloudy in the evening, becoming cloudy after midnight. Patchy light fog after midnight. A slight chance of rain in the evening, then a chance of rain after midnight. Scattered thundershowers possible. Unusually warm. Low 62°. Wind south around 10 mph, gusting to 20 mph. Chance of precipitation 50 percent. Precipitation mostly around a tenth of an inch.
Saturday
 
Cloudy in the morning, becoming mostly cloudy in the afternoon. Light to moderate fog in the morning. A chance of rain in the morning, then a slight chance of rain in the afternoon. Scattered thundershowers possible. Mild. High 64°, but temperatures falling in the afternoon. Wind west-northwest around 8 mph, gusting to 27 mph. Chance of precipitation 40 percent. Precipitation mostly less than a tenth of an inch.
Saturday night
 
Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 43°. Wind north-northwest around 2 mph, gusting to 21 mph, in the evening, becoming east-southeast after midnight.

WXSIM forecast formatting script by Saratoga-Weather.org.

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