Weather WorldUpper Flat Lake, IL Weather Forecast
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Upper Flat Lake Weather Forecast
| TONIGHT | WEDNESDAY | WEDNESDAY NIGHT | THURSDAY | THURSDAY NIGHT | FRIDAY | FRIDAY NIGHT | SATURDAY | SATURDAY NIGHT | SUNDAY | SUNDAY NIGHT | MONDAY |
 |  |  |  |  |  | | | | | | |
| Mostly Clear | Chance of T-Storm | Chance of T-Storm | Thunderstorms | Clearing | Mostly Clear | Mostly Clear | Chance of T-Storm | Chance of T-Storm | Chance of T-Storm | Chance of T-Storm | Chance of T-Storm |
| Lo: 71°FLo: 22°C | Hi: 91°FHi: 33°C | Lo: 69°FLo: 21°C | Hi: 81°FHi: 27°C | Lo: 60°FLo: 16°C | Hi: 85°FHi: 29°C Lo: 65°FLo: 18°C | Hi: 85°FHi: 29°C Lo: 65°FLo: 18°C | Hi: 89°FHi: 32°C | Lo: 65°FLo: 18°C | Hi: 85°FHi: 29°C | Lo: 65°FLo: 18°C | Hi: 89°FHi: 32°C |
| POP: 40% | POP: 70% | POP: 70% | POP: 40% | POP: 40% | POP: 40% | POP: 20% | POP: 30% |
POP = Probability of Precipitation.
Weather Outlook Updated: 617 PM CDT Tue Sep 08 2026 
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Issued: 704 PM CDT Tue Sep 8 2026
Key Messages
- It will be warm and humid again on Wednesday ahead of a cold front. However, current thinking is that clouds and afternoon showers and thunderstorms will keep heat index values below Heat Advisory criteria
- Thunderstorms on Wednesday afternoon and evening may produce gusty winds and hail. Continuing storms overnight night may produce locally heavy rainfall.
Aviation
/00Z TAFS THROUGH 06Z THURSDAY/... Issued at 621 PM CDT Tue Sep 8 2026
Dry, VFR conditions are forecast through the evening...