Last updated: August 1, 2025
Understanding the UV Index is crucial for residents and visitors in Hayakawa, Japan, especially given its temperate climate characterized by warm summers and cold winters. Awareness of UV levels is essential for preventing sunburn and maintaining skin health, as prolonged exposure can lead to serious consequences. Typically, the UV Index peaks notably around midday, reaching highs of 12, which indicates a severe risk of harm from unprotected sun exposure. As such, staying informed about daily UV levels can help you enjoy the beautiful outdoors while safeguarding your skin against potential damage.
The UV Index paints a vivid picture of the sun's intensity throughout the day. Early risers will find a gentle start at 7:00 AM with a mild UVI of 2, but as the sun climbs higher, the intensity sharply rises to 8 by 9:00 AM and peaks at a striking 12 between 11:00 AM and 12:00 PM. This aggressive UV exposure begins to taper off in the afternoon, dropping to 6 by 3:00 PM and continuing to diminish as the sun sets, with a final UVI of 0 by 7:00 PM. To stay protected during the peak hours, enjoying the outdoors between 10:00 AM and 2:00 PM requires caution—it's the sun’s strongest embrace!
| 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 | 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 |
Throughout the year, the UV Index demonstrates significant seasonal variations, highlighting the importance of sun protection during peak months. From March to August, the UV Index reaches its highest levels, peaking at 12 in June, July, and August, which falls under the extreme exposure category with a burn time of just 10 minutes. This indicates that March through August are the high-risk months for UV exposure, particularly April and May, which see indices of 10 and 11 respectively. Residents and visitors are advised to take extra precautions during these months, including wearing sunscreen, protective clothing, and seeking shade, especially during the midday hours. As the year progresses into the autumn and winter months, UV levels decrease, but awareness should still be maintained in February, October, and November, where the UV Index remains in the high range.
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 |
| Hayakawa | 4 | 7 | 9 | 10 | 11 | 12 | 12 | 12 | 10 | 7 | 6 | 4 |