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National Weather Service Forecast for: St. Charles County
Issued by: NWS National Weather Service Saint Louis, MO

Updated: 249 AM CDT Sun Aug 9 2026

St. Charles , MO

Today Sunny	Tonight Mostly Clear	Monday Hot	Monday Night Partly Cloudy	Tuesday Hot	Tuesday Night Thunder storm	Wednesday Thunder storm	Wednesday Night Thunder storm	Thursday Thunder storm
Hi ≈95°F	Lo ≈75°F	Hi ≈95°F	Lo ≈75°F	Hi ≈95°F	Lo ≈75°F	Hi ≈95°F	Lo ≈75°F	Hi ≈85°F

Today	Sunny. Highs in the mid 90s. South winds 10 to 15 mph. Heat index values up to 106 this afternoon.
Tonight	Mostly clear. Humid with lows in the mid 70s. South winds 5 to 10 mph. Heat index values up to 104 early in the evening.
Monday	Sunny, hot with highs in the mid 90s. Southwest winds 5 to 10 mph. Heat index values up to 110 in the afternoon.
Monday Night	Partly cloudy. Humid with lows in the upper 70s. Southwest winds 5 to 10 mph. Heat index values up to 109 early in the evening.
Tuesday	Sunny, hot with highs in the mid 90s. Southwest winds 5 to 10 mph. Heat index values up to 109.
Tuesday Night	Partly cloudy. A slight chance of showers and thunderstorms. Lows in the upper 70s.
Wednesday	Partly cloudy. A slight chance of showers and thunderstorms. Highs in the mid 90s.
Wednesday Night	Partly cloudy in the evening, then becoming mostly cloudy. A chance of showers and thunderstorms. Lows in the lower 70s. Chance of rain 50 percent. Heat index values up to 105 early in the evening.
Thursday	Showers and thunderstorms likely in the morning, then mostly cloudy with a chance of showers and thunderstorms in the afternoon. Highs in the upper 80s. Chance of rain 60 percent.
Thursday Night	Mostly cloudy. A chance of showers and thunderstorms in the evening, then showers and thunderstorms likely after midnight. Lows around 70. Chance of rain 70 percent.
Friday	Mostly cloudy with a chance of showers and thunderstorms. Highs in the mid 80s.
Friday Night	Mostly cloudy with a chance of showers and thunderstorms. Lows around 70.
Saturday	Mostly cloudy with a chance of showers and thunderstorms. Highs in the mid 80s.
Zone Forecast	St. Charles County

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