Last updated: June 2, 2025
Understanding the UV Index is crucial for residents and visitors of Ogasawara, Japan, where the sun's intensity can vary dramatically throughout the day. With peak UV levels reaching as high as 13 between 11:00 AM and 12:00 PM, awareness of these levels is vital for preventing sunburn and protecting skin health. Ogasawara enjoys a Cfa climate, which means warm summers and mild winters, leading to significant UV exposure even outside the summer months. By staying informed about the UV Index, you can enjoy the stunning natural beauty of these islands while safeguarding your skin from the harmful effects of UV radiation.
As the day unfolds, the UV Index peaks dramatically, revealing the sun’s intensity. At 07:00, it starts at a mild 3 but quickly escalates. By 09:00, the index reaches a striking 9, and at 10:00, it surges further to 11. The sun hits its zenith at 11:00 and 12:00, both clocking in at a thrilling 13, indicating the need for sun protection. As the afternoon progresses, the UV rays begin to wane, dropping to 11 again at 13:00, followed by a gentle decline to 8 at 14:00. An even greater drop follows, dipping to 5 at 15:00, before tapering off to a mere 1 by 17:00 and dropping to 0 by 19:00. The day's UV journey emphasizes the importance of staying vigilant under the sun’s powerful rays during peak hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 3 | moderate | 30 min |
| 08:00 | 5 | moderate | 30 min |
| 09:00 | 9 | very high | 15 min |
| 10:00 | 11 | extreme | 10 min |
| 11:00 | 13 | extreme | 10 min |
| 12:00 | 13 | extreme | 10 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 8 | very high | 15 min |
| 15:00 | 5 | moderate | 30 min |
| 16:00 | 2 | low | 45 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 0 | low | 45 min |
Throughout the year, UV exposure varies significantly, peaking during the spring and summer months. Notably, March through September experience extreme UV levels, with indices consistently reaching 12 or higher, indicating a high risk for sunburn. In particular, April to July holds the highest UV ratings, making these months crucial for sun protection. High-risk months include February to October, with a sharp increase from February's very high index of 9 to April's extreme index of 13. Residents and visitors should be particularly vigilant in these months, limiting sun exposure between 10 AM and 4 PM and utilizing sunscreen, protective clothing, and sunglasses to mitigate UV damage effectively. As UV levels decrease in November and December, while still cautioning against exposure, the risk diminishes significantly.
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 |
| 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 |
| Ogasawara | 7 | 9 | 11 | 13 | 12 | 13 | 13 | 12 | 12 | 10 | 8 | 6 |