Last updated: June 2, 2025
Understanding the UV Index in San Marcos, United States, is crucial for protecting your skin against harmful ultraviolet (UV) radiation. High UV levels can lead to sunburn and long-term skin health issues, making it essential for residents and visitors alike to stay informed about daily UV exposure risks. With San Marcos’ humid subtropical climate (Cfa), the sun’s intensity peaks during midday, especially from 11:00 AM to 2:00 PM, when the UV Index can soar to 12—a level that necessitates extra precautions. By being aware of the UV Index, you can enjoy the sunny weather while safeguarding your skin.
The UV Index throughout the day reveals a dynamic shift in sun intensity. In the early hours, from 7:00 to 9:00, the index remains low at 1 to 3, perfect for a leisurely morning stroll. However, as the sun climbs higher, the UV exposure peaks dramatically at 12:00 with an index of 10, reaching its highest point of 12 at 1:00 PM. This is the critical time for sun safety measures—sunscreen and protective clothing are essential! As the afternoon progresses, the intensity begins to wane, dropping to a 7 by 4:00 PM and further to a gentle 1 by 7:00 PM. Overall, it's a day marked by a sharp rise and gradual decline in UV levels, highlighting the importance of staying shielded during peak hours.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 3 | moderate | 30 min |
| 10:00 | 5 | moderate | 30 min |
| 11:00 | 8 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 12 | extreme | 10 min |
| 14:00 | 11 | extreme | 10 min |
| 15:00 | 10 | very high | 15 min |
| 16:00 | 7 | high | 25 min |
| 17:00 | 5 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
The UV Index exhibits significant seasonal variation, with the highest levels typically occurring from April to September. During these months, the UV Index reaches extremes of 11 to 12, categorizing them as extreme exposure. February through October are considered high-risk months, especially April to August, where the burn time is as short as 10 minutes. It is vital for residents and visitors to take precautions, such as wearing sunscreen, protective clothing, and seeking shade during peak sunlight hours to minimize the risk of skin damage. As the UV Index decreases in the fall and winter months, November and December present lower risk, with more moderate values of 6 and 5, allowing for longer exposure times before burning occurs. Adjusting outdoor activities according to the UV index is essential for ensuring safety and health throughout 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 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| San Marcos | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 12 | 11 | 9 | 6 | 5 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |