As of 1:48 PM MDT on September 12, 2026, all 2 cities in Custer County, MT in our database have a UV Index reading of Low. The city with the highest UV Index reading right now is Ismay, MT with a reading of 2.4.
Over the next 24 hours, the highest UV Index reading in Custer County, MT is expected to be 5.1 in Ismay between 12:00 PM - 1:00 PM MDT tomorrow.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |