Last updated: June 2, 2025
Understanding the UV Index in San Francisco is crucial for protecting your skin and overall health in this vibrant city. With the unique Csb climate, San Francisco can experience surprising levels of UV radiation, particularly during midday when the index peaks at 11. This awareness is essential as even brief exposure to high UV levels can lead to sunburn and increase the risk of skin damage. As locals and visitors alike explore the iconic sites under the California sun, being informed about UV levels can help ensure safe outdoor activities and promote long-term skin health. Stay protected and enjoy San Francisco’s beauty while keeping an eye on the UV Index!
The UV Index paints a vivid picture of sun intensity throughout the day. Starting off at a low 1 at 7:00 AM, the sun begins to rise, prompting a gradual increase as it climbs higher in the sky. By 9:00 AM, the index reaches 4, indicating moderate exposure. The intensity peaks sharply at 12:00 PM with a notable 10 and hits its zenith at 1:00 PM, boasting an impressive 11. As the afternoon wears on, this extreme UV exposure begins to taper off, dropping to 9 by 3:00 PM and then descending further to 2 by 6:00 PM. Finally, as twilight approaches, the index falls back to a gentle 1 by 7:00 PM. It’s a vivid reminder of the sun’s power, urging us to take precautions during those peak hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | low | 45 min |
| 09:00 | 4 | 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 | 11 | extreme | 10 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 |
Throughout the year, UV index levels exhibit significant seasonal changes, with high-risk months primarily from March to August. During this period, the UV index peaks, reaching extreme levels of 11 in June and July, where the burn time is as low as 10 minutes. Visitors and residents should take precautionary measures during these months, seeking shade and using SPF protection to reduce the risk of sunburn and long-term skin damage. Levels start to moderate again from September to November, allowing for safer sun exposure. January and December present the least risk, with moderate UV index levels of 3, where exposure can be as long as 30 minutes without immediate harm. It's essential for everyone to remain vigilant and adjust their sun safety practices based on the UV index throughout the seasons.
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 |
| San Francisco | 3 | 5 | 8 | 9 | 10 | 11 | 11 | 10 | 9 | 7 | 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 |