Last updated: June 2, 2025
Understanding the UV Index is crucial for residents and visitors of São Luís, Portugal, where the Mediterranean climate can lead to significant sun exposure. With UV levels reaching a maximum of 11 during the day, it's essential to comprehend these readings to protect your skin from harmful sunburn and long-term health issues. By being aware of the UV Index, you can make informed choices about sun protection and outdoor activities, ensuring your skin stays healthy under the bright Portuguese sun. Whether you're strolling along the beautiful coast or exploring the city, knowing when UV levels peak helps you enjoy the vibrant weather while minimizing risks.
As the sun rises, the UV Index begins at a gentle 1 at 07:00 and 08:00, indicating minimal sun exposure risk. However, by 09:00, it jumps to 3 and continues to climb rapidly, reaching a significant 8 by 11:00. High noon brings the peak UV index of 10 at 12:00, followed by an intense 11 from 13:00 to 14:00, signaling a critical time for sun protection. As the afternoon wanes, the index starts to decline, dropping to 9 at 15:00, then decreasing to 7 at 16:00 and 5 by 17:00. Post-sunset, the index falls sharply to 3 at 18:00 and settles back at 1 as the day concludes at 19:00. This data underscores the importance of staying shielded from midday sun when the UV radiation is at its strongest.
| 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 | 11 | extreme | 10 min |
| 14:00 | 11 | extreme | 10 min |
| 15:00 | 9 | very high | 15 min |
| 16:00 | 7 | high | 25 min |
| 17:00 | 5 | moderate | 30 min |
| 18:00 | 3 | moderate | 30 min |
| 19:00 | 1 | low | 45 min |
Seasonal changes in UV radiation show a significant increase from late winter through summer, peaking during the hotter months. High-risk months with extreme UV levels include June (UV Index 11) and July to August (UV Index 10), where the burn time is as little as 10 to 15 minutes. Visitors and residents should take precautionary measures during these months, such as wearing protective clothing, using broad-spectrum sunscreen, and minimizing sun exposure between 10 AM and 4 PM. As fall approaches, UV levels gradually decrease, but it remains important to stay aware, particularly in March through October, when the UV index often enters the high to very high categories.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Braga UVI | 2 | 4 | 6 | 8 | 9 | 11 | 10 | 9 | 8 | 6 | 4 | 2 |
| Porto UVI | 2 | 4 | 6 | 8 | 9 | 11 | 10 | 9 | 8 | 6 | 4 | 2 |
| Amadora UVI | 3 | 5 | 6 | 9 | 10 | 11 | 10 | 9 | 8 | 6 | 4 | 3 |
| Lisbon UVI | 3 | 5 | 6 | 9 | 10 | 11 | 10 | 9 | 8 | 6 | 4 | 3 |
| Setubal UVI | 3 | 5 | 6 | 9 | 10 | 11 | 10 | 9 | 8 | 6 | 4 | 3 |
| Sao Luis | 3 | 5 | 6 | 9 | 10 | 11 | 10 | 10 | 9 | 7 | 4 | 3 |