Viana do Castelo UV Index

Viana do Castelo, Portugal experiences significant seasonal variation in UV radiation at latitude 41.7°N. The UV index ranges from 4 in January to 11 in June, with an annual average of 7.5. This variation follows the pattern typical of mid-latitude cities.

The highest UV levels in Viana do Castelo occur in June, when the UV index reaches 11 (extreme). During this period, unprotected skin can burn in as little as 10 minutes during peak hours (11am to 3pm). SPF 50+ sunscreen, protective clothing, and seeking shade are strongly recommended.

The lowest UV levels occur in January, with an average UV index of 4 (moderate). Even during this period, UV levels are moderate and basic sun protection is advisable for prolonged outdoor exposure.

The World Health Organization recommends sun protection measures when the UV index is 3 or above. In Viana do Castelo, the UV index exceeds this threshold for 12 months of the year. For 6 months, the UV index reaches "very high" or "extreme" levels, requiring extra precautions.