Last updated: July 2, 2025
Understanding the UV Index is essential for residents and visitors in Onomichi, Japan, where the combination of its Cfa climate and the sun’s intensity can pose significant risks to skin health. With peak UV levels reaching a hazardous 12 around midday, awareness of these fluctuations is crucial for preventing sunburn and long-term skin damage. By keeping an eye on the UV Index throughout the day, you can take necessary precautions, ensuring your outdoor adventures in this picturesque coastal city are both enjoyable and safe. Regularly monitoring UV levels helps you protect your skin from harmful rays, making it a vital part of life under the Japanese sun.
The UV Index begins its rise at 7:00 AM with a low of 2, gradually climbing to a moderate 3 by 8:00 AM. By 9:00 AM, it reaches 6, but it's at 10:00 AM when the sun truly bears down, peaking at a high of 9. The intensity continues to soar, hitting a maximum of 12 at 12:00 PM, making it the most UV-active hour of the day. From there, it subtly declines, dropping back to 11 at 1:00 PM, and 9 at 2:00 PM. The afternoon brings relief as the index falls to 6 by 3:00 PM and continues to decrease, settling at 4 by 4:00 PM. As the day winds down, the UV Index dips to 2 by 5:00 PM and further to a safe 1 by 6:00 PM and stays consistent through 7:00 PM. Stay sun-smart and avoid peak UV hours for your skin's safety!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 3 | moderate | 30 min |
| 09:00 | 6 | high | 25 min |
| 10:00 | 9 | very high | 15 min |
| 11:00 | 11 | extreme | 10 min |
| 12:00 | 12 | extreme | 10 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 6 | high | 25 min |
| 16:00 | 4 | moderate | 30 min |
| 17:00 | 2 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 1 | low | 45 min |
The UV Index experiences significant seasonal fluctuations, peaking between May and August, where an extreme rating of 11 to 12 indicates a burn time of just 10 minutes. March and April also see heightened levels, categorized as very high with a burn time of 15 minutes. Conversely, the UV Index is at its lowest during January, February, and December, marked as moderate, allowing for a safer 30-minute exposure before risking sunburn. The highest-risk months for UV exposure are May to August, necessitating strong sun protection measures for visitors and residents alike. It is essential to wear sunscreen, protective clothing, and sunglasses, especially during peak hours, to minimize the risk of UV-related health issues.
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 |
| Onomichi | 4 | 5 | 8 | 10 | 11 | 11 | 12 | 12 | 10 | 7 | 6 | 4 |
| Osaka UVI | 4 | 6 | 8 | 11 | 11 | 11 | 12 | 11 | 10 | 7 | 5 | 3 |