Last updated: May 3, 2025
In Shiroishi, Japan, being aware of the UV Index is crucial for protecting your skin and overall health. The UV Index indicates the strength of ultraviolet (UV) radiation from the sun, which can lead to sunburn and long-term skin issues when exposure is not managed properly. With Shiroishi’s Cfa climate, residents and visitors experience significant UV exposure, especially during peak hours when levels soar to 10 from 11:00 AM to 12:00 PM. Understanding these UV levels helps you take proactive measures, ensuring you enjoy the sun safely while minimizing the risk of skin damage.
As the sun rises, the UV Index begins its ascent, starting at a mild 2 at 7:00 AM. By 8:00 AM, it ramps up to 4, signaling the need for some sun protection. The intensity peaks between 10:00 and 12:00, reaching a maximum of 10, meaning it’s crucial to stay shaded and apply sunscreen during these hours. The numbers start to decline after 1:00 PM, with the index dropping to 8 at 1:00 PM, then further easing to 6 at 2:00 PM, and tapering off to 4 by 3:00 PM. As the day winds down, the index falls to 1 by 5:00 PM, and eventually to 0 after sunset, reminding us that while the daytime sun can be intense, the evening cools both temperature and UV exposure.
| 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 | 10 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 8 | very high | 15 min |
| 14:00 | 6 | high | 25 min |
| 15:00 | 4 | 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, the UV Index experiences significant fluctuations, peaking during the summer months. January and December see a moderate UV Index of 3, with a burn time of 30 minutes. As early as February, the Index rises to 5, indicating a continued moderate exposure. However, March marks the onset of high risk with an Index of 7, reducing burn time to 25 minutes. The real concern arises from April to August, where the Index reaches very high (9-10) and even extreme levels (11) in July and August, with dangerously short burn times of just 10-15 minutes. The season begins to taper off in September (UV Index 9) and October (UV Index 6), before returning to moderate levels in November and December. For visitors and residents, it is crucial to take protective measures, especially from April to August, by seeking shade, wearing protective clothing, and applying sunscreen rigorously to prevent harmful UV exposure.
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 |
| Shiroishi | 3 | 5 | 7 | 9 | 10 | 10 | 11 | 11 | 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 |