Last updated: August 1, 2025
Understanding the UV Index is crucial for residents and visitors in Viana do Castelo, Portugal, where the combination of a mild maritime climate and clear summer days can lead to significant sun exposure. With UV levels peaking at 9 during midday hours, being informed can help you prevent sunburn and protect your skin health. Taking the time to monitor UV readings can make a big difference, allowing you to enjoy outdoor activities while safeguarding against the harmful effects of UV radiation. So, whether you're exploring the stunning coastline or enjoying a leisurely afternoon in the sun, staying aware of the UV Index is key to a healthy sun-safe experience in this beautiful coastal town.
The UV Index throughout the day showcases a striking peak in intensity. Early morning hours, from 07:00 to 09:00, maintain a mild level of 1 to 3, making sun protection less critical. As the clock strikes 10:00, the index rises to 4, signaling a cautionary note for sun exposure. By 11:00, it escalates dramatically to 7, and at 12:00, it reaches a blistering 8, indicating high risk. The intensity continues to soar, peaking at 9 between 13:00 and 14:00, prompting a need for robust sun safety measures. As the afternoon wanes, the UV Index gently declines to 7 at 16:00, before tapering off to 4 by 17:00, and finally receding to 1 by 19:00. This data underscores the importance of vigilant sun protection during the midday hours when UV exposure is at its highest.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 2 | low | 45 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 |