UV Index in Koshima, Japan

Last updated: June 2, 2025

Understanding the UV Index is vital for residents and visitors of Koshima, Japan, where the subtropical Cfa climate exposes individuals to varying UV levels throughout the day. With peak UV indices frequently reaching up to 12 during midday hours, awareness of these levels is essential for preventing sunburn and safeguarding skin health. Prolonged exposure to UV radiation can lead to serious health concerns, making it crucial to stay informed about the UV index as you engage in outdoor activities. Whether you’re enjoying beautiful coastal views or exploring the area’s lush landscapes, knowing the UV exposure risks can help you protect yourself and make the most of your time in this vibrant locale.

Hourly UV Index in Koshima

The UV Index for the day reveals a dynamic shift in sun exposure, peaking dramatically between 11:00 AM and 1:00 PM. Starting the morning with a mild maximum of 2 at 7:00 AM, the index steadily rises, reaching 12 by midday—an indication of high risk for harm from unprotected sun exposure. As the afternoon progresses, it dips to 10 at 2:00 PM and then gradually decreases to a more moderate level of 4 by 4:00 PM. By the evening, the UV Index settles back down to 1 by 6:00 PM, signaling a safe time to enjoy the outdoors again. Be sure to protect your skin during those 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	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	12	extreme	10 min
14:00	10	very high	15 min
15:00	7	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

Monthly UV Index Trends in Koshima

Throughout the year, the UV Index exhibits significant seasonal variations, with the highest risks occurring between March and September. During this period, particularly in June, July, and August, the UV Index reaches its peak at 13, indicating extreme exposure levels with a burn time of just 10 minutes. Conversely, the UV levels are generally moderate in January and December (UV Index 5) and high in February and November (UV Index 7), where burn times extend to 25-30 minutes. Residents and visitors are strongly advised to take precautionary measures, especially from March to September, by seeking shade, wearing protective clothing, and applying sunscreen, to reduce the risk of skin damage from UV radiation.

Monthly Maximum UV Index for Koshima, Japan

The monthly maximum UV Index (UVI) represents the highest UV radiation level recorded each month in Koshima. 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 Koshima, 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 Koshima UV Index with Other Japan Cities

The table above highlights how UV exposure in Koshima 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.

Koshima'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
Koshima	5	7	10	11	12	12	13	13	11	8	7	5