Last updated: July 2, 2025
Understanding the UV Index is crucial for residents of Butte, Montana, where the sun's rays can present significant risks, especially during peak hours. With a climate classified as Dfc, Butte faces seasonal variations in UV radiation, making it essential to be aware of daily UV levels to prevent sunburn and protect skin health. On typical summer days, UV levels can soar to 7 around midday, indicating a high risk of harm to unprotected skin. By staying informed and taking precautions, you can enjoy the outdoors safely while safeguarding your skin's health.
At dawn, the UV Index begins its ascent, peaking at 1 by 7:00 AM. As the sun rises higher, it gently climbs to 2 by 9:00 AM, but the real intensity arrives at midday. By 12:00 PM, the index reaches 6, and it continues to soar to its maximum of 7 at 1:00 PM and 2:00 PM. As the afternoon progresses, the UV levels gradually taper off, descending to 5 by 4:00 PM and finally settling back to 2 by 7:00 PM. This data highlights the importance of sun protection during peak hours, particularly between 11:00 AM and 3:00 PM, when the UV exposure is most potent.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 2 | low | 45 min |
| 10:00 | 3 | moderate | 30 min |
| 11:00 | 4 | moderate | 30 min |
| 12:00 | 6 | high | 25 min |
| 13:00 | 7 | high | 25 min |
| 14:00 | 7 | high | 25 min |
| 15:00 | 6 | high | 25 min |
| 16:00 | 5 | moderate | 30 min |
| 17:00 | 4 | moderate | 30 min |
| 18:00 | 3 | moderate | 30 min |
| 19:00 | 2 | low | 45 min |
Throughout the year, seasonal UV changes indicate varying levels of sun exposure risk. From January to February, the UV Index remains low (1), allowing for a safe exposure time of up to 45 minutes. As we transition into March, the index rises to 3, indicating a moderate risk, reducing the safe exposure time to 30 minutes. The risk peaks in May through July with high UV levels (6 and 7), necessitating an exposure limit of just 25 minutes. In August and September, the index returns to moderate levels (5 and 4), allowing for a 30-minute burn time again. As the year concludes, October through December sees a return to low UV levels (1-2), with a safe exposure limit of 45 minutes. Residents and visitors should be particularly cautious during the high-risk months of May, June, and July, applying sunscreen and seeking shade to mitigate potential sun damage.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Butte | 1 | 1 | 3 | 4 | 6 | 6 | 7 | 5 | 4 | 2 | 1 | 1 |
| 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 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |