Last updated: August 1, 2025
Understanding the UV Index is crucial for residents and visitors in Francisco Serrato (San Bartolo), Mexico, where the climate features a typical Cwb classification, bringing both sun and potential UV exposure risks. The UV levels here can soar to an extreme index of 13 during midday hours, emphasizing the importance of being mindful of sun exposure to prevent sunburn and protect overall skin health. By being aware of the UV Index, you can take proactive measures against harmful rays and enjoy the beautiful weather while keeping your skin safe.
The UV Index reveals a dramatic rise in solar intensity as the day progresses. Starting at a low value of 0 at 7:00 AM, it gently climbs to 1 by 8:00 AM. However, by 10:00 AM, the index surges to 5, signaling the onset of midday sun. The peak intensity is reached between 12:00 PM and 2:00 PM, where the UV Index hits a remarkable 13, indicating a high risk of harm from unprotected sun exposure. As the afternoon wanes, the index gradually declines, dropping to 9 by 4:00 PM and tapering down to 1 by 7:00 PM. This hourly data serves as a crucial reminder to stay protected during those peak hours, especially when the UV Index is at its highest.
| 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 | 8 | very high | 15 min |
| 12:00 | 11 | extreme | 10 min |
| 13:00 | 13 | extreme | 10 min |
| 14:00 | 14 | extreme | 10 min |
| 15:00 | 12 | extreme | 10 min |
| 16:00 | 9 | very high | 15 min |
| 17:00 | 5 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
During the year, the UV Index shows notable seasonal changes, with highest UV levels occurring from February through October. The months of March, April, May, June, July, August, and September consistently fall within the extreme exposure category, peaking at 15 in April. Visitors and residents should be particularly cautious during these high-risk months, as the burn time is as little as 10 minutes during this period. It is advised to take protective measures, such as wearing sunscreen, protective clothing, and hats, and seeking shade during peak hours to minimize the risk of sunburn. In contrast, November and December see a decrease in UV levels, categorized as very high, with a burn time of 15 minutes, suggesting a slight but essential drop in overall sun exposure risk as the year comes to a close.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Guadalajara UVI | 9 | 11 | 14 | 14 | 14 | 13 | 13 | 13 | 13 | 12 | 9 | 8 |
| Francisco Serrato (San Bartolo) | 10 | 11 | 14 | 15 | 14 | 14 | 13 | 14 | 14 | 12 | 10 | 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 |