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City of St. Charles, MOSt Charles, MO Weather Forecast
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St Charles Weather Forecast
| THIS AFTERNOON | TONIGHT | THURSDAY | THURSDAY NIGHT | FRIDAY | FRIDAY NIGHT | SATURDAY | SATURDAY NIGHT | SUNDAY | SUNDAY NIGHT | MONDAY | MONDAY NIGHT |
 |  | |  |  |  | | | |  |  | |
| Chance of T-Storm | Chance of T-Storm | Chance of T-Storm | Mostly Cloudy | Chance of Showers | Mostly Clear | Chance of T-Storm | Chance of T-Storm | Chance of T-Storm | Partly Cloudy | Partly Cloudy | Chance of T-Storm |
| Hi: 95°FHi: 35°C | Lo: 71°FLo: 22°C | Hi: 81°FHi: 27°C | Lo: 65°FLo: 18°C | Hi: 85°FHi: 29°C | Lo: 69°FLo: 21°C | Hi: 89°FHi: 32°C | Lo: 69°FLo: 21°C | Hi: 90°FHi: 32°C | Hi: 91°FHi: 33°C Lo: 71°FLo: 22°C | Hi: 91°FHi: 33°C Lo: 71°FLo: 22°C | Lo: 70°FLo: 21°C |
| POP: 40% | POP: 90% | POP: 90% | POP: 20% | POP: 50% | POP: 50% | POP: 20% | POP: 40% |
POP = Probability of Precipitation.
Weather Outlook Updated: 1103 AM CDT Wed Sep 09 2026 
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Issued: 508 AM CDT Wed Sep 9 2026
Key Messages
- An arriving cold front and increasing clouds and showers/ thunderstorms lead to uncertainty in heat index values today, but a Heat Advisory has been issued for southeastern MO and southwestern IL where confidence is highest in 105+ F values.
- Showers and thunderstorms will be widespread at times this evening through Thursday morning. The strongest thunderstorms this evening may be capable of gusty to perhaps damaging winds. Locally heavy rainfall is possible overnight, but confidence ...