Last updated: May 3, 2025
Understanding the UV Index is essential for residents and visitors in Yokohama, Japan, where the climate typically falls within the Dfb zone. The UV Index provides a daily measure of the sun's strength, helping you assess the risk of overexposure to harmful ultraviolet rays—crucial for preventing sunburn and maintaining skin health. With peak UV levels reaching a high of 9 between 11:00 AM and 12:00 PM, residents should be particularly aware of their sun exposure during these hours to minimize potential risks. Be proactive in protecting your skin while enjoying Yokohama’s beautiful outdoor spaces!
As the sun rises, the UV Index begins its ascent, peaking at 11:00 AM and 12:00 PM with a blistering 9. The day starts gently, with 07:00 AM registering a modest 2, but by 09:00 AM, it climbs to a moderate 6. The intensity escalates, hitting 8 at 10:00 AM and reaching its zenith shortly after noon. After this peak, the index gradually dips, easing down to 6 by 2:00 PM, before falling further to 4 at 3:00 PM. As evening approaches, the UV radiation wanes significantly, dropping to 2 by 4:00 PM and near zero after sunset, signaling a shift in the skies. Remember to protect your skin during those peak hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 4 | moderate | 30 min |
| 09:00 | 6 | high | 25 min |
| 10:00 | 8 | very high | 15 min |
| 11:00 | 9 | very high | 15 min |
| 12:00 | 9 | very high | 15 min |
| 13:00 | 8 | very high | 15 min |
| 14:00 | 6 | high | 25 min |
| 15:00 | 4 | moderate | 30 min |
| 16:00 | 2 | low | 45 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 0 | low | 45 min |
The UV Index varies significantly throughout the year, reflecting seasonal changes in sun exposure. High-risk months for UV radiation include late spring and summer, specifically from April to August, when levels reach very high to extreme ratings, making burn times as low as 10 to 15 minutes. Visitors and residents should be particularly vigilant during these months; protective measures, such as wearing sunscreen, hats, and sunglasses, are essential. January through March and October exhibit moderate to high UV levels, where burn times range from 25 to 30 minutes, while November and December present lower UV risks with longer burn times of 30 to 45 minutes. It’s advisable to monitor local UV forecasts and adjust outdoor activities accordingly to minimize skin damage.
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 | 4 | 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 |