Last updated: July 2, 2025
In Oshu, Japan, being aware of the UV Index is crucial for safeguarding your skin and overall health. Understanding the varying UV levels throughout the day can help prevent painful sunburns and long-term skin damage, making it essential for both locals and visitors alike. With a Cfa climate, Oshu experiences a range of UV exposures, peaking around midday with an Index hitting 10, indicating very high risk. By staying informed about UV levels, you can enjoy the outdoors while effectively protecting yourself from the sun’s harmful rays.
During the day, the UV Index experiences a dynamic shift, peaking in the late morning. Starting at 3 at 07:00, it escalates to reach a high of 10 by 11:00 and remains there until 12:00. As afternoon approaches, the index gradually declines, dropping back to 9 by 13:00, then to 7 at 14:00. By the mid to late afternoon, it continues its descent, falling to 5 at 15:00 and further down to 3 by 16:00. In the evening, the index diminishes significantly, plummeting to 1 at both 17:00 and 18:00, and finally reaching 0 by 19:00. This pattern highlights the importance of sun protection during the peak hours of 10:00 to 12:00 when the UV radiation is most intense.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 3 | moderate | 30 min |
| 08:00 | 5 | moderate | 30 min |
| 09:00 | 7 | high | 25 min |
| 10:00 | 9 | very high | 15 min |
| 11:00 | 10 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 9 | very high | 15 min |
| 14:00 | 7 | high | 25 min |
| 15:00 | 5 | moderate | 30 min |
| 16:00 | 3 | moderate | 30 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 0 | low | 45 min |
Throughout the year, seasonal changes in UV Index highlight varying levels of sun exposure risk. From January to February, the UV Index remains in the moderate range (3-4), allowing for a burn time of 30 minutes. A noticeable increase starts in March with the index rising to 6 (high), decreasing burn time to 25 minutes. April through September marks the high-risk months, where the index spikes to very high levels (8-10), significantly reducing burn time to just 15 minutes. Following September, October sees a drop back to high (6), allowing for a slightly safer exposure of 25 minutes, before returning to moderate levels (3-4) in the final months. Visitors and residents are advised to take precautions during high UV months from March to September, including wearing protective clothing, using sunscreen, and seeking shade to minimize the risk of skin damage.
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 |
| Oshu | 3 | 4 | 6 | 8 | 9 | 10 | 10 | 10 | 9 | 6 | 4 | 3 |
| 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 |