Last updated: June 2, 2025
Understanding the UV Index is crucial for residents and visitors of Yokohama, Japan, where the humid subtropical climate can lead to significant sun exposure. With UV levels peaking at a striking 11 during midday hours, awareness of UV intensity is vital for preventing sunburn and protecting skin health. This knowledge not only helps in planning your outdoor activities but also plays a key role in minimizing long-term skin damage. As you explore the vibrant city of Yokohama, being informed about the UV Index can enhance your outdoor experience while keeping your skin safe from the sun's harmful rays.
As the day unfolds, the UV Index begins to climb, starting at a mild 2 by 07:00. By 08:00, it ascends to a moderate 5, indicating that sun protection becomes essential. The intensity peaks at 11 between 11:00 and 12:00, marking the hours when solar radiation is most potent. Following this peak, the index gradually declines; it drops to 10 at 13:00, before descending to 7 by 14:00. The afternoon sees a further decrease, with readings of 5 at 15:00 and 3 at 16:00—perfect for those wishing to enjoy the sun while still being cautious. By 17:00, the index falls to a mild 1, and as the day winds down, it reaches 0 by 19:00, signaling a retreat from the sun's harmful rays. It’s crucial to stay informed and protect your skin during peak UV hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 5 | 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 |
As the seasons change, the UV Index fluctuates significantly, influencing the risk of sun exposure throughout the year. January and February start with a moderate UV Index of 3 and 5, allowing for a burn time of 30 minutes. However, by March, the UV Index jumps to 8, which is categorized as very high, reducing safe exposure to just 15 minutes. The peak months for UV radiation are May through August, where the Index reaches an extreme level of 11, necessitating a mere 10 minutes of exposure before risking sunburn. September begins a gradual decline to a very high index of 10, while October and onward return to moderate levels. Visitors and residents should be particularly cautious from March to August—wearing protective clothing, applying sunscreen, and seeking shade to minimize UV damage during these high-risk months.
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 | 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 |