Last updated: July 2, 2025
Understanding the UV Index is essential for staying safe and healthy in Porto, Brazil, where the sun can be intense, especially during the midday hours. High UV levels can lead to painful sunburns and long-term skin damage, making it crucial to monitor daily exposure. Porto's tropical climate brings a unique blend of warmth and humidity, heightening the risk of UV radiation, particularly between 10 AM and 2 PM when the index peaks at 11. By staying informed about UV levels, residents and visitors can enjoy the vibrant outdoor lifestyle Porto offers, while minimizing the risks associated with sun exposure.
The UV Index throughout the day paints a vivid picture of solar intensity, peaking sharply in the late morning. At 07:00, the UV Index starts off modestly at 1, but by 08:00, it climbs to 3, indicating a gradual increase in sunlight. As the day progresses, it reaches 5 at 09:00 and then escalates dramatically to 8 by 10:00. The sun's strength hits its zenith at 11:00 with a striking 10, peaking even further at 12:00, where it soars to 11—an optimal time for sun protection. After this high, the UV Index begins to wane, falling back to 10 at 13:00, before declining steadily to 4 at 15:00, 2 at 16:00, and eventually drifting down to 1 by 17:00. As dusk approaches, the UV Index drops to 0 by 18:00, signaling a safe end to sun exposure for the day. Such daily fluctuations highlight the importance of being mindful of UV levels, especially during midday hours.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 3 | moderate | 30 min |
| 09:00 | 5 | moderate | 30 min |
| 10:00 | 8 | very high | 15 min |
| 11:00 | 10 | very high | 15 min |
| 12:00 | 11 | extreme | 10 min |
| 13:00 | 10 | very high | 15 min |
| 14:00 | 7 | high | 25 min |
| 15:00 | 4 | moderate | 30 min |
| 16:00 | 2 | low | 45 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 0 | low | 45 min |
| 19:00 | 0 | low | 45 min |
The UV Index shows an extreme risk of harm from unprotected sun exposure throughout the year, with very high levels observed from January to March, peaking at 16 in March. This indicates that the sun’s rays can cause skin burn in as little as 10 minutes. April maintains a high UV Index of 15, and while there is a slight decrease in June and July (both at 11), the exposure risk remains severe. August and September return to a UV Index of 13, continuing the call for diligent sun protection. As October progresses to 12 and into the late autumn months, visitors and residents should still remain vigilant, especially since November and December retain a UV Index of 13. To minimize risk, it is essential for everyone to apply sunscreen, wear protective clothing, and seek shade during peak sun hours throughout all seasons.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rio de Janeiro UVI | 15 | 14 | 13 | 10 | 7 | 6 | 7 | 9 | 11 | 12 | 13 | 15 |
| Sao Paulo UVI | 16 | 15 | 12 | 11 | 8 | 6 | 7 | 9 | 11 | 13 | 14 | 15 |
| Belo Horizonte UVI | 17 | 16 | 14 | 12 | 9 | 7 | 8 | 10 | 12 | 13 | 14 | 16 |
| Salvador UVI | 14 | 14 | 14 | 13 | 10 | 9 | 9 | 12 | 12 | 15 | 15 | 14 |
| Fortaleza UVI | 14 | 14 | 15 | 15 | 13 | 11 | 11 | 12 | 13 | 13 | 13 | 13 |
| Porto | 14 | 14 | 16 | 15 | 13 | 11 | 11 | 13 | 13 | 12 | 13 | 13 |