Last updated: August 1, 2025
Understanding the UV Index in Joetsu, Japan is crucial for protecting your skin and overall health. With Japan's Cfa climate, characterized by warm summers and mild winters, UV levels can soar to dangerous heights, especially between 10 AM and 2 PM. Awareness of the UV Index helps you gauge exposure, allowing you to take preventative measures against sunburn and long-term skin damage. For residents and visitors alike, knowing when UV levels peak—reaching a high of 11 during midday—can make all the difference in safeguarding your skin against harmful rays. Stay informed and enjoy the beautiful outdoors safely!
The UV Index exhibits a dynamic pattern throughout the day, peaking impressively at 12:00 PM with a striking value of 11, indicating a very high risk of harm from unprotected sun exposure. As early as 9:00 AM, the index jumps to 7, suggesting it’s time to start applying sunscreen. The intensity swells to 10 by 11:00 AM, urging sun safety measures. After reaching its zenith, the index gradually declines, dipping to 5 by 3:00 PM and eventually settling at a low of 0 by 7:00 PM. With these fluctuations, it’s crucial to be sun-smart, especially during peak hours!
| 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 | 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 |
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 |