Last updated: May 3, 2025
Understanding the UV Index in Tamalpais-Homestead Valley is crucial for protecting your skin and overall health. With UV levels peaking at a high of 10 around midday, awareness of these fluctuations can help residents take necessary precautions against sunburn and long-term skin damage. Nestled in a mild Csb climate, this charming valley experiences significant UV exposure, especially during the summer months. By staying informed about the UV Index, you can enjoy the beautiful outdoors while ensuring your skin remains safe and healthy.
As the sun rises, the UV Index begins its gradual ascent, starting at a mild 1 at 07:00. By 08:00, it reaches 2, indicating a low risk, perfect for morning strolls. The intensity picks up at 09:00, hitting 3, and then surges to 6 by 10:00. From 11:00 to 13:00, the index escalates dramatically, peaking at an intense 10, marking the hours when sun protection is crucial. The afternoon maintains this peak, with 10 persisting until 14:00. As the day progresses, the evening brings relief; the index drops to 8 at 15:00, and gradually declines to 3 by 17:00, and finally retreats to 1 by 19:00. This hourly data highlights the importance of seeking shade and using sunscreen during midday hours to ensure safety under the sun.
| 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 | 10 | very high | 15 min |
| 14:00 | 10 | very high | 15 min |
| 15:00 | 8 | very high | 15 min |
| 16:00 | 6 | high | 25 min |
| 17:00 | 3 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
The UV Index exhibits significant seasonal variation, peaking during the summer months and dramatically declining in winter. From January to February, the UV Index ranges from 3 to 5, classified as moderate, allowing for around 30 minutes of safe sun exposure. However, March to June sees a sharp increase, reaching an extreme level of 11 in both June and July, where unprotected skin can burn in just 10 minutes. The high-risk months for UV exposure are therefore March through August, where the index remains predominantly high to extreme. As a result, it is crucial for visitors and residents to take protective measures during these months, such as wearing sunscreen, protective clothing, and seeking shade, especially during peak hours. From September to December, while the UV Index decreases, users should still remain vigilant, as moderate levels persist late in the year.
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 |
| Tamalpais-Homestead Valley | 3 | 5 | 8 | 9 | 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 |