As of 1:21 PM MDT on September 18, 2025, all 5 cities in Custer County, ID in our database have a UV Index reading of High. The city with the highest UV Index reading right now is Mackay, ID with a reading of 6.9.
Over the next 24 hours, the highest UV Index reading in Custer County, ID is expected to be 7.1 in Clayton between 2:00 PM - 3:00 PM MDT today.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |