Last updated: July 2, 2025
Understanding the UV Index is crucial for residents and visitors in Kosai, Japan, where the subtropical climate brings intense sun exposure, especially during peak hours. Keeping track of UV levels is essential for preventing sunburn and promoting long-term skin health; awareness can significantly reduce the risk of skin damage, even on seemingly mild days. With UV Index values soaring to 12 during midday, Kosai's sunny disposition comes with potential risks, making it vital to stay informed and safeguard your skin against harmful radiation. Enjoy the beautiful outdoor activities Kosai offers, but remember to check the UV Index regularly for safe sun exposure!
Starting off the day, the UV Index begins at a modest 2 at 07:00, gradually rising to a moderately high 4 by 08:00. As the sun climbs higher, the intensity peaks with a striking 12 at 12:00, marking the sun’s strongest rays. The Index remains remarkably high, peaking at 11 from 11:00 to 13:00, prompting sun safety precautions. By 14:00, the value drops to 8, then continues to decline, ending the day at a minimal 0 by 19:00. With this data, it's clear that the sun calls for protection during the midday hours, especially between 10:00 and 13:00, making sunscreen and shade a must for outdoor activities!
| 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 | 10 | very high | 15 min |
| 11:00 | 11 | extreme | 10 min |
| 12:00 | 12 | extreme | 10 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 8 | very high | 15 min |
| 15:00 | 6 | high | 25 min |
| 16:00 | 3 | moderate | 30 min |
| 17:00 | 2 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 0 | low | 45 min |
The UV Index experiences significant seasonal variation, with March through September being the high-risk months for sun exposure. March begins the rise with an index of 8 (very high) and only a 15-minute burn time, peaking in July with an index of 12 (extreme) and a mere 10-minute burn time. May through August consistently holds an extreme exposure category, urging increased caution during these months. As summer transitions into fall, the index gradually decreases, with October dropping to 7 (high) and 15-minute burn times for October and September, before returning to moderate levels in winter. Visitors and residents are advised to take precautions during the high-risk months by seeking shade, wearing protective clothing, and applying sunscreen regularly to minimize the risk of skin damage.
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 |
| Kosai | 4 | 5 | 8 | 10 | 11 | 11 | 12 | 11 | 10 | 7 | 5 | 4 |
| Osaka UVI | 4 | 6 | 8 | 11 | 11 | 11 | 12 | 11 | 10 | 7 | 5 | 3 |