Last updated: May 3, 2025
Understanding the UV Index is crucial for residents and visitors of Koya, Japan, where the lush greenery of this scenic town conceals potential UV hazards. Given the region's Cfa climate—characterized by warm summers and mild winters—it's essential to recognize the varying levels of UV radiation throughout the day to prevent sunburn and protect your skin health. With peak UV levels soaring to 11 around noon, awareness and proactive measures become vital for enjoying the outdoors safely while minimizing skin damage. Stay informed about UV exposure risks to ensure your time in Koya is both enjoyable and safe!
The UV Index throughout the day reveals a dramatic rise in sun intensity, peaking during the late morning to early afternoon. Starting the day at a modest 2 at 7:00 AM, the index climbs steadily, reaching 11 by 11:00 AM and maintaining that level until 1:00 PM. This signifies a high risk of harm from unprotected sun exposure. Following this peak, the index begins to dip, dropping to 8 by 2:00 PM, and continuing its decline until it falls to 0 by 7:00 PM. With this information, it's crucial to take sun safety precautions—especially during the hours when the UV Index is at its highest!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 4 | moderate | 30 min |
| 09:00 | 6 | high | 25 min |
| 10:00 | 9 | 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 | 8 | very high | 15 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, UV exposure varies significantly, with the highest risk occurring during the late spring and summer months. From April to August, the UV Index peaks at 11 to 12, representing an extreme exposure category, with a rapid burn time of just 10 minutes. Notably, March and September are also high-risk months, with UV Index levels of 8 and 10, respectively. To protect against harmful UV radiation, it is essential for both visitors and residents to take precautions during these peak months: seek shade, wear protective clothing, and apply broad-spectrum sunscreen regularly, especially between 10 AM and 4 PM. In contrast, during the winter months (January, December), UV levels drop to moderate, offering lower risk for skin damage, with 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 |
| Koya | 4 | 6 | 8 | 11 | 11 | 11 | 12 | 12 | 10 | 7 | 6 | 4 |