Last updated: May 3, 2025
Understanding the UV Index is crucial for residents and visitors in Viana do Castelo, Portugal, as it provides vital information about the intensity of ultraviolet radiation and its potential impact on skin health. With the region's Csb climate—characterized by mild, wet winters and warm, dry summers—UV exposure can peak as high as 9 during the midday hours, significantly increasing the risk of sunburn and long-term skin damage. By staying informed about UV levels, you can take proactive steps to protect your skin while enjoying the beauty of Viana do Castelo, ensuring a safe and enjoyable outdoor experience year-round.
Starting from 07:00 AM, the UV Index remains low at 1, perfect for a morning stroll. As the sun climbs higher, the intensity gradually increases: reaching 3 by 09:00 AM and then escalating to 4 at 10:00 AM. The peak intensity occurs at 01:00 PM, with a striking UV Index of 9, suggesting it's vital to seek shade or apply sunscreen during this hour. The afternoon sees a slight decline, with values of 8 at 03:00 PM and 6 by 04:00 PM. As the day winds down, the UV Index drops back to 4 at 05:00 PM, and then gently falls to 2 by 06:00 PM, before settling back at 1 near sunset. It's a day to stay sun-smart!
| 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 | 4 | moderate | 30 min |
| 11:00 | 6 | high | 25 min |
| 12:00 | 8 | very high | 15 min |
| 13:00 | 9 | very high | 15 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 8 | 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 experiences significant seasonal fluctuations, with the highest levels typically occurring from April to August. During this peak period, the UV Index reaches very high levels, particularly in June with a maximum of 10, indicating a burn time of only 15 minutes. March marks the transition to higher risk, classified as high, with a UV Index of 6 and a burn time of 25 minutes. Conversely, the winter months of January and December show a low UV Index of 2, allowing for extended exposure of up to 45 minutes without risk of burns. Given this data, it is crucial for visitors and residents to take extra precautions during April to August by wearing sunscreen, protective clothing, and limiting sun exposure during peak hours to minimize the risk of skin damage.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Viana do Castelo | 2 | 4 | 6 | 8 | 9 | 10 | 9 | 9 | 7 | 6 | 3 | 2 |
| 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 |