As of 8:09 AM CDT on September 20, 2026, all 7 cities in Johnson County, IL in our database have a UV Index reading of Low. The city with the highest UV Index reading right now is Vienna, IL with a reading of 0.3.
Over the next 24 hours, the highest UV Index reading in Johnson County, IL is expected to be 6.8 in Vienna between 1:00 PM - 2:00 PM CDT today.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |