Last updated: July 2, 2025
Understanding the UV Index in Ishii, Japan is crucial for safeguarding your skin and overall health. The UV Index provides vital information about the strength of ultraviolet radiation on any given day, helping residents and visitors prevent sunburn and long-term skin damage. Given Ishii’s Cfa climate, which features hot summers and mild winters, UV exposure can peak significantly, especially during midday hours when the index reaches levels as high as 12. Being aware of the UV levels and taking appropriate precautions can make a big difference in enjoying the beautiful outdoor activities Ishii has to offer while keeping your skin healthy and protected.
The UV Index throughout the day exhibits a dramatic rise, peaking at 12 around noon. Starting from a humble 2 at 7:00 AM, the intensity steadily climbs as the sun ascends. By 10:00 AM, it reaches 9, signaling that sun protection is essential. The zenith occurs at 11:00 AM with a staggering 11, followed closely by 12 at noon, making it crucial to seek shade and wear sunscreen. The index begins to taper off in the afternoon, descending to 6 by 3:00 PM, and then falls further to 1 as evening sets in. This trend underscores the importance of monitoring UV levels to ensure safe sun exposure at its peak.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 4 | moderate | 30 min |
| 09:00 | 7 | high | 25 min |
| 10:00 | 9 | very high | 15 min |
| 11:00 | 11 | extreme | 10 min |
| 12:00 | 12 | extreme | 10 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 9 | 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 levels vary significantly, with the highest risks typically occurring in the late spring to summer months. From April through August, the UV Index reaches extreme levels of 11 to 12, indicating that even short exposure (as little as 10 minutes) can result in skin damage. The highest-risk months are April, May, June, July, and August, where it's crucial for both visitors and residents to take protective measures such as wearing sunscreen, hats, and protective clothing. As summer transitions to fall, UV levels begin to decline, with an Index of 10 in September, followed by 7 in October and 6 in November. Visitors and residents should remain vigilant, especially during these peak months, to ensure their safety and well-being under the sun. In the winter months (December and January), the UV Index drops to 4, indicating a moderate risk, allowing for longer burn times of 30 minutes.
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 |
| Ishii | 4 | 6 | 8 | 11 | 11 | 12 | 12 | 12 | 10 | 7 | 6 | 4 |