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City of Mt. Vernon, IllinoisMount Vernon, IL Weather Forecast
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Mount Vernon Weather Forecast
| THIS AFTERNOON | TONIGHT | MONDAY | MONDAY NIGHT | TUESDAY | TUESDAY NIGHT | WEDNESDAY | WEDNESDAY NIGHT | THURSDAY | FRIDAY | FRIDAY NIGHT | SATURDAY |
 |  |  |  |  | |  | | | |  | |
| Mostly Sunny | Chance of T-Storm | Chance of T-Storm | Partly Cloudy | Partly Sunny | Partly Cloudy | Partly Cloudy | Partly Cloudy | Partly Cloudy | Partly Cloudy | Mostly Cloudy | Mostly Cloudy |
| Hi: 95°FHi: 35°C | Lo: 69°FLo: 21°C | Hi: 81°FHi: 27°C | Lo: 61°FLo: 16°C | Hi: 79°FHi: 26°C | Hi: 75°FHi: 24°C Lo: 55°FLo: 13°C | Hi: 75°FHi: 24°C Lo: 55°FLo: 13°C | Lo: 55°FLo: 13°C | Hi: 79°FHi: 26°C Lo: 55°FLo: 13°C | Hi: 79°FHi: 26°C Lo: 55°FLo: 13°C | Hi: 80°FHi: 27°C Lo: 55°FLo: 13°C | Hi: 80°FHi: 27°C Lo: 55°FLo: 13°C |
| POP: 50% | POP: 50% |
POP = Probability of Precipitation.
Weather Outlook Updated: 127 PM CDT Sun Sep 20 2026 
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Issued: 611 PM CDT Sun Sep 20 2026
Key Messages
- The Heat Advisory comes to an end at 7 PM this evening. Most locations will experience 95 to 100 degree heat indices this afternoon.
- The heat is off! A cold front will usher in much cooler air to the region, as it moves through tonight. Temperatures for the next week should be near normal with highs near 80 and lows in the upper 50s.
- An area of showers and thunderstorms will spread east along the I-64 corridor late tonight into Monday morning. Another area will spread east across the...