St. Marys, IL Weather Forecast
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St. Marys Weather Forecast
| REST OF TONIGHT | THURSDAY | THURSDAY NIGHT | FRIDAY | FRIDAY NIGHT | SATURDAY | SUNDAY | SUNDAY NIGHT | MONDAY | MONDAY NIGHT | TUESDAY | TUESDAY NIGHT |
| Mostly Cloudy | Chance of T-Storm | Chance of T-Storm | Showers | Partly Cloudy | Mostly Clear | Mostly Clear | Clear | Clear | Clear | Clear | Mostly Clear |
| Lo: 69°FLo: 21°C | Hi: 89°FHi: 32°C | Lo: 61°FLo: 16°C | Hi: 69°FHi: 21°C | Lo: 49°FLo: 9°C | Hi: 71°FHi: 22°C Lo: 49°FLo: 9°C | Hi: 71°FHi: 22°C Lo: 49°FLo: 9°C | Hi: 70°FHi: 21°C Lo: 49°FLo: 9°C | Hi: 70°FHi: 21°C Lo: 49°FLo: 9°C | Hi: 69°FHi: 21°C Lo: 41°FLo: 5°C | Hi: 69°FHi: 21°C Lo: 41°FLo: 5°C | Hi: 75°FHi: 24°C Lo: 45°FLo: 7°C |
| POP: 20% | POP: 100% | POP: 70% |
POP = Probability of Precipitation.
Weather Outlook Updated: 127 AM CDT Thu Oct 01 2026 

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Issued: 301 AM CDT Thu Oct 1 2026
Key Messages
- Multiple rounds of widespread rain will track across the region this afternoon through Friday morning. Broad rainfall totals of 0.25 to 0.75 inches are expected, though localized heavy rain bands could produce isolated amounts of 2 to 3 inches.
- Temperatures drop significantly heading into the weekend, with highs in the upper 60s Friday and Saturday, and overnight lows falling into the 40s.
- Crisp, quiet autumn weather will remain across the region through early next week before temper...
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