UV Index in Yokohama Today
September 4, 2026 · Yokohama, Japan
3,574,443 people
See today's UV index in Yokohama hour by hour below. The UV index shows how strong the sun's ultraviolet radiation is — the higher the number, the faster skin can burn. Values are calculated for Yokohama's coordinates and updated daily.
UV has dropped for today
Hour by hour
Clouds cut the peak by ~52%Protection windowClear sky
Remember today
- Sunscreen SPF 30+
- Sunglasses
Daylight: sunrise 05:16 – sunset 18:07
Tomorrow: UV 4 at its peak around 09:00
The UV index in Yokohama peaks at 4 (moderate) around 11:00 today. Sun protection is recommended between 09:40 and 11:41, while the index stays at 3 or above. Cloud cover is damping the peak by roughly 52% compared with a clear sky. Tomorrow the index is forecast to peak at 4 around 09:00.
UV index in Yokohama hour by hour
| Time | UV index | Level |
|---|---|---|
| 05:00 | 0 | Low |
| 06:00 | 0.1 | Low |
| 07:00 | 0.3 | Low |
| 08:00 | 0.9 | Low |
| 09:00 | 2 | Low |
| 10:00 | 3.5 | Moderate |
| 11:00 | 4.1 | Moderate |
| 12:00 | 2.5 | Low |
| 13:00 | 1.8 | Low |
| 14:00 | 1.5 | Low |
| 15:00 | 0.8 | Low |
| 16:00 | 0.3 | Low |
| 17:00 | 0.1 | Low |
| 18:00 | 0 | Low |
| 19:00 | 0 | Low |
UV index in Yokohama
Yokohama lies at 35°N. The midday sun reaches 61.9° above the horizon in Yokohama today, against a yearly ceiling of 78.0°. Elevation is what sets the ceiling for UV, and over Yokohama it is high enough for the index to reach very high values through the summer months.
What is the UV index?
The UV index is an international scale describing the strength of the sun's ultraviolet radiation at ground level. It starts at 0 and is effectively open-ended — at mid-latitudes it rarely exceeds 8, while in the tropics and high in the mountains it can pass 11. The higher the number, the less time it takes to get sunburnt.
The UV index depends mainly on how high the sun is in the sky. That is why it peaks around solar noon and is greatest in summer near the longest day of the year. Clouds, ozone, altitude and reflection from snow or water also affect the value.
The WHO UV scale
| UV index | Level | Recommendation |
|---|---|---|
| 0–2 | Low | No special protection needed. |
| 3–5 | Moderate | Use sunscreen (SPF 30+), seek shade around midday. |
| 6–7 | High | Sunscreen, hat and sunglasses. Avoid the sun 12:00–15:00. |
| 8–10 | Very high | Extra protection. Limit midday sun exposure. |
| 11+ | Extreme | Avoid the sun at midday. Full protection required. |