Weather World
Cornwall, IL Weather Forecast
Quick Weather Clicks
Settings
Sun & Moon
Cornwall Weather Forecast
| REST OF TODAY | TONIGHT | SATURDAY | SATURDAY NIGHT | SUNDAY | SUNDAY NIGHT | MONDAY | TUESDAY | WEDNESDAY | WEDNESDAY NIGHT | THURSDAY |
 |  | |  | | |  | | |  | |
| Sunny | Partly Cloudy | Sunny | Mostly Clear | Mostly Sunny | Partly Cloudy | Partly Cloudy | Partly Cloudy | Partly Cloudy | Chance of Showers | Mostly Sunny |
| Hi: 95°FHi: 35°C | Lo: 71°FLo: 22°C | Hi: 91°FHi: 33°C | Lo: 69°FLo: 21°C | Hi: 85°FHi: 29°C | Hi: 85°FHi: 29°C Lo: 65°FLo: 18°C | Hi: 85°FHi: 29°C Lo: 65°FLo: 18°C | Hi: 91°FHi: 33°C Lo: 75°FLo: 24°C | Hi: 91°FHi: 33°C Lo: 75°FLo: 24°C | Lo: 70°FLo: 21°C | Hi: 85°FHi: 29°C |
| POP: 40% |
POP = Probability of Precipitation.
Weather Outlook Updated: 916 AM CDT Fri Sep 04 2026 
Cornwall Radar Loop
Use the map search tool if you want to place a location marker on the radar map...
Cornwall Weather Map
Cornwall Quick Facts
Cornwall Forecast Discussion
Meteorlogic Glosserator
Instant definitions for any meteorological term.
Instant definitions for any meteorological term.
Issued: 616 AM CDT Fri Sep 4 2026
Key Messages
- Impactful heat will continue across the area through Saturday with peak heat indices of 100 to 110. The heat warnings may need to be expanded Saturday into the I-80 corridor east of the Quad Cities.
- There will be brief reprieves from the heat late this weekend and late next week. Another surge of heat and humidity with heat indices around 100 is expected the middle of next week. The overall pattern has a 55-70% probability of above normal temperatures through mid- September.
- There is...