Last updated: June 2, 2025
Understanding the UV Index is crucial for residents and visitors of Kurayoshi, Japan, where the subtropical climate brings long, sunny days. With UV levels peaking around midday, reaching as high as 11—a level that can cause severe sunburn in mere minutes—awareness is essential for sunburn prevention and maintaining optimal skin health. By staying informed about daily UV exposure risks, you can protect yourself and enjoy the beautiful outdoor landscape while minimizing potential skin damage. Remember, even when the sun seems less intense, harmful UV rays can still pose a threat!
The UV Index paints a vivid picture of the sun’s strength throughout the day. Starting at a modest 2 at 07:00, the index gradually climbs as the sun ascends, reaching 4 by 08:00. By 09:00, it spikes to 6, and before long, it peaks at an impressive 11 at 12:00, marking the most intense exposure. The afternoon starts to cool slightly, with the index dropping to 10 by 13:00 and then tapering off through 8 at 14:00, 6 at 15:00, and back to 4 at 16:00. As the sun begins its descent, the UV Index falls to 2 by 17:00, lingering at 1 through the evening hours, creating a gentle reminder to enjoy the sun but also to stay mindful of its intensity during peak hours.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 4 | moderate | 30 min |
| 09:00 | 6 | high | 25 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 | 8 | very high | 15 min |
| 15:00 | 6 | high | 25 min |
| 16:00 | 4 | moderate | 30 min |
| 17:00 | 2 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, UV exposure significantly varies, peaking during the summer months of June through August, when the UV Index reaches extreme levels between 11 and 12 and the burn time drops to just 10 minutes. The high-risk months are particularly from April to September, where UV levels rise to very high to extreme values, requiring heightened awareness for sun protection. Visitors and residents should adopt protective measures, such as wearing sunscreen, hats, and sunglasses, especially during the peak UV hours from 10 a.m. to 4 p.m. Conversely, the winter months from December to February present a lower risk with a UV Index between 3 and 5. Although the risk decreases, it's still important to remain cautious, as UV radiation can still cause skin damage even on cloudy days.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sapporo UVI | 2 | 3 | 6 | 7 | 9 | 9 | 9 | 10 | 8 | 5 | 3 | 2 |
| Yokohama UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Tokyo UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Kurayoshi | 4 | 5 | 7 | 10 | 10 | 11 | 12 | 11 | 10 | 7 | 5 | 3 |
| Nagoya UVI | 4 | 6 | 8 | 10 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 3 |
| Osaka UVI | 4 | 6 | 8 | 11 | 11 | 11 | 12 | 11 | 10 | 7 | 5 | 3 |