Last updated: June 2, 2025
Understanding the UV Index is crucial for residents and visitors of Hayama, Japan, where the mild Cfa climate offers plenty of opportunities for outdoor activities. With peak UV levels often soaring to 11 during midday, awareness of these fluctuations is essential not only for sunburn prevention but also for long-term skin health. By grasping the significance of UV levels, individuals can take appropriate precautions against harmful exposure, especially considering the region's typical summer conditions and reflective coastal surfaces that amplify UV risks. Stay informed, protect your skin, and enjoy the beautiful beaches of Hayama responsibly!
As the day unfolds, the UV Index rises sharply, peaking during the midday hours. At 07:00, it begins at a modest 2, but by 09:00, it escalates to 7, urging outdoor enthusiasts to take precautions. The sun reaches its zenith between 10:00 and 12:00, with the index soaring to a maximum of 11—a clear signal for sun safety measures. As the afternoon progresses, the intensity diminishes; by 14:00, it drops to 7, and further declines to 5 by 15:00. As daylight wanes, the index continues to fall, resting at 1 by 17:00 and tapering off to 0 post 19:00. This rhythmic rise and fall of UV exposure highlights the importance of midday vigilance against harmful rays.
| 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 | 10 | 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 |
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 |
| Hayama | 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 |