Last updated: May 3, 2025
Understanding the UV Index is crucial for the residents and visitors of San Guillermo, Mexico, where the BSh climate – characterized by hot and dry conditions – can lead to elevated sun exposure. Knowing the UV levels throughout the day helps in making informed decisions about sun protection, which is essential for preventing sunburn and safeguarding skin health. With the UV Index peaking at a striking 13 around noon, it's vital to stay vigilant and take precautions to enjoy the beautiful sunny days while minimizing the risks associated with harmful UV radiation.
At sunrise, the UV Index begins softly at 1 around 7:00 AM, gradually rising to 2 by 8:00 AM. As the day progresses, it quickly gains intensity, hitting 4 at 9:00 AM and soaring to 7 by 10:00 AM. The peak unfolds between 11:00 AM and 1:00 PM, with a blistering maximum of 13. Following this zenith, the index starts its decline, dropping to 12 at 2:00 PM and gradually easing down to 10 by 3:00 PM. The late afternoon sees a gentle fall, with values of 6 at 4:00 PM, 4 by 5:00 PM, and returning to 2 and 1 as dusk approaches, reminding us of the day's shifts in sun strength. Stay protected 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 | 7 | high | 25 min |
| 11:00 | 10 | very high | 15 min |
| 12:00 | 13 | extreme | 10 min |
| 13:00 | 13 | extreme | 10 min |
| 14:00 | 12 | extreme | 10 min |
| 15:00 | 10 | 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 |
The UV Index exhibits significant seasonal changes, with the highest values recorded from March to September, indicating months of extreme exposure. Specifically, March through August all register a UV Index of 13, while September is slightly lower at 12. The high-risk months for sun exposure are February through October, particularly noting March to July as critical periods due to their extreme exposure category and a burn time of just 10 minutes. Residents and visitors should take precautions during these months by seeking shade, wearing protective clothing, and applying broad-spectrum sunscreen regularly to reduce the risk of sunburn and long-term skin damage. In contrast, January and December have a 6 UV Index, while November and October see a decline to 8 and 10 respectively, indicating some respite from the sun's intensity.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| San Guillermo | 6 | 9 | 11 | 13 | 13 | 13 | 13 | 13 | 12 | 10 | 8 | 6 |
| 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 |