Last updated: July 2, 2025
Understanding the UV Index is crucial for residents of Knoxville, United States, where the sun's rays can be particularly intense during the summer months. This index provides vital information about the strength of ultraviolet radiation on any given day, helping individuals make informed decisions to protect their skin health and prevent painful sunburns. With Knoxville's humid subtropical climate characterized by warm summers and ample sunshine, UV exposure risks can be higher, especially between 10 AM and 2 PM when the UV Index peaks at levels as high as 11. Staying aware of these UV levels empowers you to enjoy outdoor activities while safeguarding your skin from potential harm.
As the sun rises, the UV Index starts off gently at 1 by 7:00 AM, gradually climbing as the day progresses. By 10:00 AM, it reaches 6, signaling a notable increase in solar radiation. The intensity peaks at 12:00 PM with a striking 10 and continues to soar to a maximum of 11 at 1:00 PM, marking the hour of greatest exposure. As the afternoon unfolds, the index begins to taper off—dropping to 10 at 2:00 PM and 8 by 3:00 PM. By late afternoon, the UV Index gracefully descends to 4 at 5:00 PM, settling back to 2 by 6:00 PM and finally returning to a gentle 1 by 7:00 PM. This highlights the importance of sun protection during mid-day when UV rays are at their most intense.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | low | 45 min |
| 09:00 | 3 | moderate | 30 min |
| 10:00 | 6 | high | 25 min |
| 11:00 | 8 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 10 | very high | 15 min |
| 15:00 | 8 | very high | 15 min |
| 16:00 | 6 | high | 25 min |
| 17:00 | 4 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
The UV Index shows significant seasonal changes, peaking during the summer months. January and December have a moderate UV Index of 3, allowing for prolonged exposure without risk of sunburn (30 minutes). As we transition into March, the risk increases with a high UV Index of 6 and a reduced burn time of 25 minutes. April through July are the highest risk months, with the UV Index reaching an extreme 11 in both June and July, allowing for just 10 minutes of safe exposure. During these months, it is crucial for both visitors and residents to take precautions such as wearing sunscreen, protective clothing, and seeking shade. As the summer fades into August and September, the UV Index remains very high at 9 and 8, but burn times extend to 15 minutes. As we move into the fall and winter, the UV levels decline, returning to moderate levels by November. Visitors and residents should stay alert to these changes throughout the year to ensure proper sun safety.
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 |
| Knoxville | 3 | 5 | 6 | 8 | 9 | 11 | 11 | 9 | 8 | 6 | 4 | 3 |
| 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 |