Last updated: July 2, 2025
In Challis, United States, being aware of the UV Index is crucial for maintaining skin health and preventing sunburn. The UV Index provides a clear indication of the sun's intensity, guiding residents and visitors to protect themselves during peak hours of exposure, especially between 11:00 AM and 3:00 PM, when levels can soar to 11—indicating extreme risk. With Challis's Dfb climate, characterized by distinct seasonal changes, understanding these UV levels is essential to avoid harmful effects from sun exposure. Stay informed and take proactive measures to enjoy the outdoors safely!
As the sun rises, the UV Index starts off low at 1 by 07:00, making it a safe time for outdoor activities. By 09:00, it rises to 3, signaling increasing sunlight. The real surge hits at 10:00 with a 5, reaching 8 by 11:00—a clear indication that sun protection is becoming necessary. The peak intensity arrives at 12:00, reaching a scorching 10, and continues to soar to an intense 11 from 13:00 to 14:00. As the afternoon rolls in, the index begins to dip slightly to 10 by 15:00, and further declines to 8 by 16:00. Finally, as the day unwinds, the UV levels decrease to 5 at 17:00, then settle at 3 and 2 by 18:00 and 19:00, respectively. Stay sun-smart during those peak hours to protect your skin!
| 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 | 8 | very high | 15 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 | 8 | very high | 15 min |
| 17:00 | 5 | moderate | 30 min |
| 18:00 | 3 | moderate | 30 min |
| 19:00 | 2 | low | 45 min |
Throughout the year, UV exposure varies significantly, with the highest risk months typically from March to August. During this period, the UV Index peaks at 11, indicating an extreme exposure category in May, June, and July, where a burn can occur in as little as 10 minutes. Visitors and residents should take extra precautions during these months, such as seeking shade, wearing protective clothing, and applying sunscreen regularly. As summer transitions into fall, UV levels gradually decrease, but September still presents a very high risk with an index of 9. Conversely, winter months, especially December and January, exhibit much lower UV indices, ranging from 2 to 3, which means prolonged exposure is less of a concern. Overall, being UV-aware and practicing sun safety is crucial during the high-risk months.
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 |
| Challis | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 10 | 9 | 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 |