UV Index in Koya, Japan

Last updated: June 2, 2025

Understanding the UV Index is crucial for residents and visitors in Koya, Japan, where the climate presents unique sun exposure challenges. With the UV levels peaking at an intense 11 during midday hours, being aware of these fluctuations is essential for preventing sunburn and promoting long-term skin health. Koya's Cfa climate means that even on cloudy days, harmful UV rays can penetrate, making it vital to prioritize sun safety. Whether you're exploring the serene temples or hiking scenic trails, knowing the UV Index helps you enjoy the outdoors while protecting your skin.

Hourly UV Index in Koya

As the sun rises, the UV Index begins at a mild 2 by 07:00. It steadily escalates, reaching 4 at 08:00, and then surges to a peak of 11 between 11:00 and 12:00—this is when the sun is most intense. Vigilance is essential during these hours, as the risk of skin damage increases significantly. As the afternoon progresses, the UV levels gradually decline; 10 at 13:00, followed by a decrease to 8 at 14:00, a more manageable 6 at 15:00, and finally tapering off to 3 by 16:00. By 17:00, the index drops to 2, and the evening settles in with a minimal 1 by 18:00 and 19:00. It's a day of high UV exposure, urging outdoor enthusiasts to take precautions during peak hours.

Average solar exposure data for the current time of the year. Actual values may vary and depend on many factors, such as cloud cover, vegetation cover, surface type, etc.
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	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	8	very high	15 min
15:00	6	high	25 min
16:00	3	moderate	30 min
17:00	2	low	45 min
18:00	1	low	45 min
19:00	1	low	45 min

Monthly UV Index Trends in Koya

Throughout the year, UV exposure varies significantly, with the highest risk occurring during the late spring and summer months. From April to August, the UV Index peaks at 11 to 12, representing an extreme exposure category, with a rapid burn time of just 10 minutes. Notably, March and September are also high-risk months, with UV Index levels of 8 and 10, respectively. To protect against harmful UV radiation, it is essential for both visitors and residents to take precautions during these peak months: seek shade, wear protective clothing, and apply broad-spectrum sunscreen regularly, especially between 10 AM and 4 PM. In contrast, during the winter months (January, December), UV levels drop to moderate, offering lower risk for skin damage, with longer burn times of 30 minutes.

Monthly Maximum UV Index for Koya, Japan

The monthly maximum UV Index (UVI) represents the highest UV radiation level recorded each month in Koya. It measures the strength of ultraviolet radiation from the sun and helps assess the risk of sunburn and UV-related health issues.

Data source: Statistical UV Index data for Koya, based on information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

Compare Koya UV Index with Other Japan Cities

The table above highlights how UV exposure in Koya compares to other major locations across Japan. This comparison helps travelers and residents better understand regional sun intensity and plan outdoor activities with sun safety in mind.

Koya's solar exposure compared to other cities in Japan. Generated using Copernicus Atmosphere Monitoring Service information.
	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
Koya	4	6	8	11	11	11	12	12	10	7	6	4