Last updated: May 3, 2025
Understanding the UV Index is crucial for residents and visitors of Seiro, Japan, where the climate features warm summers and mild winters typical of a Cfa climate zone. Awareness of UV levels is essential, as high exposure can lead to sunburn and long-term skin damage. From the peak UV Index reaching 9 around noon to the fluctuating levels throughout the day, knowing when to seek shade or apply sunscreen can significantly impact your skin health. As Seiro experiences consistent sunlight, especially during the summer months, staying informed about UV exposure risks is key to enjoying the outdoors safely.
The UV Index rises steadily throughout the morning, starting at a manageable 2 at 7:00 AM. As the sun climbs higher, it peaks at an intensity of 9 between 10:00 AM and 12:00 PM, signaling a time when sun protection is essential. The index begins to taper off after 1:00 PM, dropping to 4 by 3:00 PM and further declining to 1 by 5:00 PM, indicating a safer environment for outdoor activities as evening approaches. Notably, after 7:00 PM, the UV Index drops to 0, marking the end of sun-induced UV exposure for the day. Stay vigilant during those peak hours for your skin's safety!
| 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 | 9 | very high | 15 min |
| 12:00 | 9 | 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 |
The UV Index experiences significant seasonal variation, peaking during the summer months. March marks the start of heightened UV exposure with an index of 7, classifying it as high, while April and May see values rise to 8 and 9, respectively, both categorized as very high. The summer months of June and July maintain a UV Index of 10, followed by an intense peak of 11 in August, reaching the extreme category. These months represent the highest risk for sunburn, with recommended burn times decreasing to just 10-15 minutes. As the season transitions to fall in September, the UV Index decreases slightly to 9, but remains very high, making it essential for visitors and residents to take precautions, such as applying sunscreen and wearing protective clothing. By October, UV levels drop to 6 (high), and continue to decrease through the winter months, where January and December present moderate exposure with an index of 3. Overall, it’s crucial for everyone to stay informed and protect their skin during high-risk months from March to September.
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 |
| Seiro | 3 | 4 | 7 | 8 | 9 | 10 | 10 | 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 |