Last updated: August 1, 2025
Understanding the UV Index is crucial for residents of Hiranai, Japan, as it plays a pivotal role in protecting skin health and preventing sunburn. With the region's Cfa climate, basking in the sun can be a delightful experience, yet it comes with its own set of risks—especially during peak UV levels, which can reach a staggering 10 around midday. By staying informed about these UV levels, individuals can take necessary precautions and enjoy outdoor activities without compromising their skin. Whether you're planning a beach day or a casual stroll, knowing the UV Index helps you safeguard your skin against harmful exposure.
During the early morning hours, the UV Index starts off mild, peaking at 3 by 7:00 AM. As the sun climbs higher, the intensity increases, hitting 4 by 8:00 AM and dramatically soaring to a peak of 10 at both 11:00 AM and 12:00 PM. This high level indicates a very high risk for harm from unprotected sun exposure. The afternoon brings a gradual decline, with the index dropping to 9 at 1:00 PM before easing down to 5 by 3:00 PM. As the sun sets, the UV Index gently recedes to 1 by 5:00 PM, ultimately falling to 0 by 7:00 PM, signaling a safe end to UV exposure for the day. Stay protected when the index is high, and enjoy the sun responsibly!
| 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 | 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 |
During the year, the UV Index exhibits significant seasonal fluctuations, with the highest levels occurring in summer months. From April to August, the UV Index reaches very high to extreme levels, peaking at 11 in August, where the recommended burn time is as little as 10 minutes. The high-risk months for UV exposure are April through August, necessitating extra precautions for both visitors and residents. To protect against harmful effects, individuals should wear protective clothing, apply sunscreen generously, and seek shade during peak sun hours. In contrast, January and December present lower UV indices, categorizing exposure as low, with longer burn times of up to 45 minutes. Staying informed about these changes can help ensure safe time spent outdoors throughout the year.
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 |
| Hiranai | 2 | 3 | 5 | 8 | 9 | 10 | 10 | 11 | 8 | 6 | 4 | 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 |