As of 11:50 AM MDT on July 6, 2026, all 3 cities in Grand County, UT in our database have a UV Index reading of High. The city with the highest UV Index reading right now is Thompson Springs, UT with a reading of 6.8.
Over the next 24 hours, the highest UV Index reading in Grand County, UT is expected to be 10.7 in Castle Valley between 1:00 PM - 2:00 PM MDT today.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |