As of 2:49 PM CDT on July 15, 2026, all 16 cities in Williamson County, IL in our database have a UV Index reading of Very High. The city with the highest UV Index reading right now is Pittsburg, IL with a reading of 9.2.
Over the next 24 hours, the highest UV Index reading in Williamson County, IL is expected to be 10.3 in Marion between 1:00 PM - 2:00 PM CDT tomorrow.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |