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Rend Lake, IL Weather Forecast
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Rend Lake Weather Forecast
| TODAY | TONIGHT | WEDNESDAY | WEDNESDAY NIGHT | THURSDAY | THURSDAY NIGHT | FRIDAY | SATURDAY | SATURDAY NIGHT | SUNDAY | SUNDAY NIGHT | MONDAY |
 |  | |  | | | | | |  |  |  |
| Sunny | Mostly Clear | Mostly Sunny | Clearing | Sunny | Mostly Clear | Mostly Clear | Mostly Clear | Partly Cloudy | Chance of Showers | Chance of Showers | Chance of Showers |
| Hi: 99°FHi: 37°C | Lo: 71°FLo: 22°C | Hi: 99°FHi: 37°C | Lo: 71°FLo: 22°C | Hi: 99°FHi: 37°C | Hi: 95°FHi: 35°C Lo: 71°FLo: 22°C | Hi: 95°FHi: 35°C Lo: 71°FLo: 22°C | Hi: 95°FHi: 35°C Lo: 71°FLo: 22°C | Lo: 70°FLo: 21°C | Hi: 89°FHi: 32°C Lo: 65°FLo: 18°C | Hi: 89°FHi: 32°C Lo: 65°FLo: 18°C | Hi: 81°FHi: 27°C |
| POP: 30% | POP: 30% | POP: 30% |
POP = Probability of Precipitation.
Weather Outlook Updated: 912 AM CDT Tue Sep 15 2026 
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Issued: 531 AM CDT Tue Sep 15 2026
Key Messages
- A dangerous late season heat wave with high temperatures near or at record levels will begin today and continue through most of the week.
- A Heat Advisory will be in effect this afternoon through Wednesday evening for the entire area. The Heat Advisory may need to be extended to Thursday or Friday as well.
- Cooler and less humid conditions will arrive Sunday and Monday, along with a 20 to 40% chance of showers and thunderstorms on both days.
Discussion
... Issued at 1052 PM CDT Mon Sep 1...