Last updated: May 3, 2025
Understanding the UV Index is crucial for residents and visitors in Isumi, Japan, where sun exposure can vary throughout the day. Awareness of UV levels not only helps prevent painful sunburns but also plays a vital role in maintaining long-term skin health. With Isumi's Cfa climate, characterized by warm summers and moderate UV exposure, it's important to stay informed about daily UV risks. During peak hours, particularly between 11:00 AM and 1:00 PM, the UV Index surges to dangerously high levels of 11, indicating a significant risk of harm from unprotected sun exposure. By monitoring the UV Index, you can take proactive measures to protect your skin and enjoy the beautiful outdoors safely.
As the sun rises, the UV Index begins its ascent, starting at a modest 2 at 07:00. The real intensity kicks in by 10:00, peaking at an impressive 11 from 11:00 to 12:00, signaling the need for sun protection. After the midday sun, the index gradually declines, dipping to 4 by 15:00 before sliding down to 1 by 17:00. As the evening approaches, the UV rays fade to 0 by 19:00, marking a safe end to outdoor activities. This data underscores the importance of staying sun-safe during the peak hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 5 | moderate | 30 min |
| 09:00 | 7 | high | 25 min |
| 10:00 | 10 | very high | 15 min |
| 11:00 | 11 | extreme | 10 min |
| 12:00 | 11 | extreme | 10 min |
| 13:00 | 9 | very high | 15 min |
| 14:00 | 7 | 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 |
As the UV Index fluctuates throughout the year, residents and visitors should be particularly cautious during the high-risk months of March through August, when the UV Index reaches very high to extreme levels. In these months, the burn time decreases significantly to just 10-15 minutes. Specifically, May through August shows a consistent UV Index of 11, indicating extreme risk. Conversely, from January to February and in November to December, the UV Index is at a more moderate level (4-5), allowing for longer exposure times of 30 minutes. It is advisable to take protective measures such as wearing sunscreen, hats, and sunglasses, especially during midday hours when UV radiation is strongest. By staying informed and prepared, individuals can enjoy their time outdoors while minimizing the risk of UV-related health issues.
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 |
| Isumi | 4 | 5 | 8 | 10 | 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 |