Last updated: July 2, 2025
Understanding the UV Index is crucial for residents and visitors of Rancho Tehama Reserve, where typical Csa climate conditions can lead to high levels of ultraviolet exposure. As UV levels peak around midday, reaching a maximum of 11 at 1:00 PM, awareness of these levels is vital to prevent sunburn and maintain skin health. The combination of sunny weather and elevated UV readings can pose significant risks, making it essential to stay informed and take protective measures against harmful rays while enjoying the beautiful outdoors.
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 |
Throughout the year, UV exposure varies significantly, with high-risk months typically occurring from March to August. In March, the UV Index escalates to 7 (high exposure), prompting a burn time of only 25 minutes. By April, it jumps to 8 (very high), and in May through July, it peaks at an extreme 11, where just 10 minutes of exposure can lead to sunburn. As summer wanes, August and September still present risks with indexes of 10 and 9, respectively. After October, the UV levels drop, with November and December returning to a moderate exposure category. Residents and visitors are advised to wear sunscreen, seek shade, and wear protective clothing, especially during the peak months of May through August, to minimize the risk of UV-related health issues.
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 |
| Rancho Tehama Reserve | 3 | 4 | 7 | 8 | 11 | 11 | 11 | 10 | 9 | 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 |