Last updated: July 2, 2025
Understanding the UV Index is crucial for residents and visitors in Guerneville, United States, where the cool Mediterranean climate can often mask the sun's intensity. With peak UV levels reaching 11 around midday, awareness of these values is essential for protecting yourself from sunburn and promoting long-term skin health. In a place renowned for its beautiful outdoor activities, it’s vital to remain vigilant about the risks of UV exposure, especially during the summer months when the sun is most potent. Equip yourself with the knowledge of the UV Index to enjoy Guerneville's stunning nature while safeguarding your skin!
The UV Index for today shows a dramatic rise as the sun ascends into the sky. Starting at a mild 1 by 07:00, the index gradually builds, reaching 3 by 09:00 and peaking at an intense 11 at 13:00—a level where sun protection is crucial. From this pinnacle, the values start to decline, tapering off to 10 at 14:00 and then gradually decreasing through the afternoon and evening, with values of 6 at 16:00 and sliding down to 1 by 19:00. Plan your outdoor activities accordingly, and remember to protect your skin during those peak hours!
| 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 | 9 | 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 |
As the seasons change, so does the UV Index, reflecting the risk of UV exposure throughout the year. January and December see a moderate UV Index of 3, allowing for a burn time of 30 minutes. However, from February to March, the UV levels rise significantly, peaking at 11 during the summer months of June and July, categorized as extreme, with the shortest burn time of only 10 minutes in peak months like June. The high-risk months for UV exposure are clearly April to August, when the UV Index reaches very high to extreme levels. It is advisable for visitors and residents to take necessary precautions, such as wearing sunscreen, protective clothing, and limiting sun exposure during peak hours, especially from late spring to mid-summer. As fall approaches, the risk decreases, with the UV Index dropping back to moderate levels by November.
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 |
| Guerneville | 3 | 5 | 7 | 8 | 10 | 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 |