As of 9:29 AM CDT on October 28, 2026, all 40 cities in McHenry County, IL in our database have a UV Index reading of Low. The city with the highest UV Index reading right now is Crystal Lake, IL with a reading of 0.4.
Over the next 24 hours, the highest UV Index reading in McHenry County, IL is expected to be 3.1 in Crystal Lake 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 |