Last updated: June 2, 2025
Understanding the UV Index is crucial for residents and visitors in San Francisco, Mexico, where sun exposure can lead to serious skin health issues. By keeping an eye on UV levels, you can effectively prevent sunburn and protect your skin from long-term damage. San Francisco's diverse climate, often influenced by its geographical features, presents unique UV exposure risks, particularly during midday when the index peaks at 13. Awareness of these daily fluctuations not only safeguards your health but also enhances your overall enjoyment of San Francisco's beautiful outdoor attractions.
The UV Index throughout the day follows a striking trend, starting from a minimum of 0 at 7:00 AM and gradually climbing as the sun rises. By 10:00 AM, it reaches a moderate 4, but the real intensity kicks in between 12:00 PM and 2:00 PM, peaking at an alarming 13 at 2:00 PM. This indicates that sun protection is crucial during these hours, as the UV rays are at their strongest. As the afternoon progresses, the index begins to dip, dropping to 10 at 4:00 PM and further to 6 at 5:00 PM, before cooling off to 3 by 6:00 PM and finally settling at a safe 1 by 7:00 PM. For anyone planning outdoor activities, understanding this UV Index pattern is essential for enjoying the sun wisely and safely.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 0 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 2 | low | 45 min |
| 10:00 | 4 | moderate | 30 min |
| 11:00 | 6 | high | 25 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 12 | extreme | 10 min |
| 14:00 | 13 | extreme | 10 min |
| 15:00 | 12 | extreme | 10 min |
| 16:00 | 10 | very high | 15 min |
| 17:00 | 6 | high | 25 min |
| 18:00 | 3 | moderate | 30 min |
| 19:00 | 1 | low | 45 min |
The UV Index exhibits significant seasonal variation, with the highest levels occurring from March to October, where exposure categories reach extreme status. March through August sees consistently high UV Index ratings of 12-13, resulting in a minimal burn time of just 10 minutes. Visitors and residents should be particularly cautious during these months, as the risk of sunburn is substantial. January and February also pose a risk with UV Index values near 10, categorized as very high, leading to a burn time of 15 minutes. As the seasons transition into November and December, the UV Index drops, but care should still be exercised. November has a UV Index of 9 (very high) with a burn time of 15 minutes, and December sees a further decrease to 7 (high), allowing for a slightly longer burn time of 25 minutes. To ensure safety, it is advisable to wear sunscreen, seek shade, and wear protective clothing during the high-risk months, especially from March to October when sun exposure can lead to serious skin damage in a short amount of time.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| San Francisco | 8 | 10 | 12 | 13 | 13 | 13 | 12 | 13 | 12 | 11 | 9 | 7 |
| Guadalajara UVI | 9 | 11 | 14 | 14 | 14 | 13 | 13 | 13 | 13 | 12 | 9 | 8 |
| Iztapalapa UVI | 10 | 12 | 14 | 15 | 14 | 14 | 14 | 14 | 14 | 12 | 10 | 8 |
| Ecatepec de Morelos UVI | 10 | 12 | 14 | 15 | 15 | 14 | 14 | 13 | 14 | 12 | 10 | 8 |
| Mexico City UVI | 10 | 12 | 14 | 15 | 15 | 14 | 14 | 13 | 14 | 12 | 10 | 8 |
| Puebla UVI | 10 | 12 | 14 | 15 | 15 | 15 | 15 | 14 | 14 | 13 | 10 | 9 |