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National Weather Service Forecast for: St. Charles County
Issued by: NWS National Weather Service Saint Louis, MO
Updated: 238 PM CDT Wed Sep 16 2026
St. Charles , MO
 
Tonight


Thunder storm
Thunder storm		 Thursday


Hot
Hot		 Thursday
Night

Mostly Clear
Mostly Clear		 Friday


Hot
Hot		 Friday
Night

Mostly Clear
Mostly Clear		 Saturday


Hot
Hot		 Saturday
Night

Thunder storm
Thunder storm		 Sunday


Thunder storm
Thunder storm		 Sunday
Night

Thunder storm
Thunder storm
Lo ≈75°F Hi ≈95°F Lo ≈75°F Hi ≈95°F Lo ≈75°F Hi ≈95°F Lo ≈75°F Lo ≈75°F Lo ≈65°F

 

Tonight
 
 Mostly cloudy with scattered thunderstorms with a slight chance of showers this evening, then mostly clear after midnight. Lows in the mid 70s. South winds around 5 mph. Chance of rain 40 percent.
Thursday
 
 Sunny, hot with highs in the upper 90s. West winds around 5 mph. Heat index values up to 107.
Thursday Night
 
 Mostly clear. Humid with lows in the lower 70s. Northeast winds around 5 mph. Heat index values up to 102 early in the evening.
Friday
 
 Sunny, hot with highs in the mid 90s. East winds around 5 mph, becoming south in the afternoon. Heat index values up to 105 in the afternoon.
Friday Night
 
 Mostly clear. Lows in the lower 70s. Southeast winds around 5 mph. Heat index values up to 100 early in the evening.
Saturday
 
 Mostly sunny. Hot with highs in the upper 90s.
Saturday Night
 
 Partly cloudy. A chance of showers with a slight chance of thunderstorms. Lows in the lower 70s. Highs in the lower 90s..
Sunday
 
 Partly cloudy. A chance of showers with a slight chance of thunderstorms. Lows in the lower 70s. Highs in the lower 90s..
Sunday Night
 
 Partly cloudy in the evening, then becoming mostly cloudy. A slight chance of thunderstorms in the evening. A slight chance of showers. Lows in the upper 60s. Chance of rain 20 percent.
Monday
 
 Partly sunny. A slight chance of showers in the morning, then a chance of showers with a slight chance of thunderstorms in the afternoon. Highs in the upper 80s. Chance of rain 40 percent.
Monday Night
 
 Mostly cloudy with a chance of showers in the evening, then partly cloudy with a slight chance of showers after midnight. Lows in the mid 60s. Chance of rain 40 percent.
Tuesday
 
 Partly cloudy with a 20 percent chance of showers. Highs in the lower 80s.
Tuesday Night
 
 Partly cloudy with a 20 percent chance of showers. Lows in the lower 60s.
Wednesday
 
 Partly cloudy with a 20 percent chance of showers. Highs in the lower 80s.
Zone Forecast
 
 St. Charles County

 

Forecast from NOAA-NWS for St. Charles County. (Zone forecast)