Last updated: May 3, 2025
In Joetsu, Japan, staying informed about the UV Index is key to protecting your skin and overall health. Understanding UV levels can significantly reduce the risk of sunburn and long-term skin damage, especially during the peak exposure hours from 10 AM to 2 PM when the index reaches a high of 10. With Joetsu's humid subtropical climate, it's crucial to be aware of these risks, as sunny days can result in increased UV radiation. By keeping an eye on the UV Index, residents and visitors can enjoy the outdoors safely while prioritizing their skin health.
The UV Index paints a vivid picture of the sun’s intensity throughout the day. At sunrise (07:00), the index starts modestly at 2, but by 08:00, it rises to a comfortable 4. The sun gains strength, with readings escalating to 6 by 09:00. The peak arrives at 11:00 and 12:00, where the index reaches a striking 10—a clear signal to seek shade or apply sunscreen! As the afternoon progresses, we see a decline; the UV Index drops to 9 at 13:00 and gradually decreases to 5 by 15:00. The late afternoon brings a gentle taper off to 3 by 16:00, before plummeting to 1 by 17:00 and finally settling at 0 as evening descends (19:00). Stay sun-smart and enjoy the daylight safely!
| 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 | 10 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 9 | 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 |
The UV Index exhibits significant seasonal variation, peaking during the summer months. High-risk months, particularly from March to August, see the UV Index reach extremes, with levels of 8 to 11 categorized as very high to extreme, resulting in quick burn times ranging from 10 to 15 minutes. Visitors and residents should take precautions during these months by seeking shade, wearing protective clothing, and applying sunscreen to minimize sun exposure. The UV levels decrease from September to November, but caution is still advised, especially with a moderate UV Index in the cooler months. Stay informed and protect your skin to enjoy the outdoors safely 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 |
| Joetsu | 3 | 5 | 8 | 9 | 10 | 11 | 11 | 11 | 9 | 6 | 5 | 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 |