Last updated: July 2, 2025
Understanding the UV Index in Shiojiri, Japan, is crucial for maintaining skin health and preventing sunburn. With typical UV levels peaking around midday, when the index can soar to 12, residents and visitors alike must be vigilant about sun protection, especially during the summer months characteristic of the Dfb climate. By staying informed about the daily UV forecast, you can take proactive measures to safeguard your skin against harmful ultraviolet rays, ensuring that outdoor activities in this picturesque region are both enjoyable and safe. Whether you're exploring Shiojiri's beautiful landscapes or simply soaking up the sun, being aware of UV levels will help you make informed choices for your health.
As the sun rises, the UV Index begins its ascent, reaching maximum levels early in the day. At 07:00, it starts at a mild 2, but by 08:00, it spikes to 5. The peak occurs between 11:00 and 12:00, when the index hits its highest at 12, indicating a significant potential for skin damage without protection. The afternoon sees a gradual decline; it drops to 8 by 14:00 and continues to lessen, settling at 6 by 15:00, before tapering off to 3 at 16:00, and then further to 1 by 18:00. As the day winds down, the UV Index finally drops to a safe 0 by 19:00, reminding us of the importance of sun protection during those 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 | 12 | 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 |
Throughout the year, UV index levels fluctuate, with the most significant increases occurring from March to September. During these months, particularly in May, June, July, and August, the UV index reaches its peak at 12, categorized as extreme, with a burn time of just 10 minutes. March and April also present high risks, featuring very high UV levels of 9 and 10 respectively. Visitors and residents should be particularly vigilant in these high-risk months, applying sunscreen, wearing protective clothing, and seeking shade whenever possible. As UV levels decrease from late summer into fall and winter, with January and December categorized as having moderate exposure (UV index 4), precautions remain advisable to ensure skin protection year-round.
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 |
| Shiojiri | 4 | 6 | 9 | 10 | 11 | 11 | 12 | 12 | 10 | 7 | 5 | 4 |