Last updated: July 2, 2025
Understanding the UV Index is crucial for residents and visitors in Helena, Montana. As the sun rises higher and the UV levels fluctuate throughout the day, being aware of these changes can significantly aid in sunburn prevention and the long-term health of your skin. With Helena's Cfa climate, characterized by warm summers and varying levels of sunlight, the UV Index can reach dangerously high levels, peaking at 11 around midday. Therefore, monitoring the UV Index helps ensure that you enjoy the beautiful outdoor activities this region has to offer while protecting your skin from harmful ultraviolet rays.
The UV Index for the day starts gently, with values peaking at 1 from 7:00 AM to 8:00 AM. As the sun rises higher, the index escalates, reaching 3 by 9:00 AM. A significant surge occurs between 10:00 AM and 2:00 PM, where it escalates dramatically, peaking at a striking 11 from 1:00 PM to 2:00 PM—a clear indication to seek shade and protect your skin. The afternoon sees a gradual decline, with figures dropping to 10 at 3:00 PM, then to 7 at 4:00 PM. As the day winds down, the UV Index returns to safer levels, resting at 1 by 7:00 PM. Keep in mind, high UV levels call for precautions, especially in the midday sun!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 3 | moderate | 30 min |
| 10:00 | 5 | moderate | 30 min |
| 11:00 | 7 | high | 25 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 11 | extreme | 10 min |
| 15:00 | 10 | very high | 15 min |
| 16:00 | 7 | high | 25 min |
| 17:00 | 5 | moderate | 30 min |
| 18:00 | 3 | moderate | 30 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, the UV Index exhibits significant seasonal changes, with the highest levels occurring in May, June, and July, where it reaches an extreme index of 11. These months pose the greatest risk for sunburn, with a quick burn time of just 10 minutes. The high-risk months to be particularly cautious are March through August, as the UV Index remains very high to extreme during this period. Visitors and residents should take proactive measures, including wearing protective clothing, applying broad-spectrum sunscreen, and seeking shade during peak sunlight hours, especially from 10 a.m. to 4 p.m. Conversely, in the winter months of December and January, the UV Index is lower at 3-4, indicating a moderate risk with a burn time of 30 minutes, allowing for slightly more leeway in sun exposure. Regardless of the season, it is essential to stay informed and protect yourself from harmful UV rays.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chicago UVI | 3 | 4 | 6 | 8 | 9 | 10 | 10 | 9 | 8 | 6 | 4 | 2 |
| Brooklyn UVI | 3 | 5 | 6 | 8 | 10 | 10 | 9 | 9 | 8 | 6 | 4 | 2 |
| New York City UVI | 3 | 5 | 6 | 8 | 10 | 10 | 9 | 9 | 8 | 6 | 4 | 2 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| Helena | 4 | 6 | 8 | 10 | 11 | 11 | 11 | 10 | 9 | 7 | 5 | 3 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |