UV Index in Nagano, Japan

Last updated: June 2, 2025

In Nagano, Japan, where the climate is classified as Dfb (humid continental), understanding the UV Index is essential for maintaining your skin health and preventing sunburn. With summer months often bringing elevated UV levels — peaking at a strong 11 between 11:00 AM and 1:00 PM — staying informed about UV exposure can help you take proactive measures against skin damage. The varying UV index throughout the day underscores the importance of monitoring conditions as you enjoy the beautiful outdoors, especially when planning activities that can expose you to direct sunlight. Embrace the natural beauty of Nagano while protecting your skin!

Hourly UV Index in Nagano

The UV Index showcases an intense midday sun, peaking at 11 between 11:00 AM and 12:00 PM. As the day progresses, the UV levels rise quickly; from a mild 2 at 07:00 AM, they soar to 9 by 10:00 AM, reflecting an increasing urgency for sun protection. The midday hours are particularly critical, where skin can suffer damage after just 15 minutes of exposure. After 2:00 PM, there’s a gradual decline in UV intensity, dropping to 5 by 3:00 PM, then to a safer 2 by 5:00 PM, finally decreasing to 0 after 6:00 PM. This data emphasizes the importance of staying mindful of UV exposure, especially during the 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	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	8	very high	15 min
15:00	5	moderate	30 min
16:00	3	moderate	30 min
17:00	2	low	45 min
18:00	1	low	45 min
19:00	0	low	45 min

Monthly UV Index Trends in Nagano

Throughout the year, UV radiation levels fluctuate significantly, impacting exposure risks for visitors and residents. The high-risk months for UV exposure are March through August, where the UV Index reaches very high to extreme levels, particularly peaking at an Index of 11 during May to August, allowing for a burn time of just 10 minutes. In contrast, the moderate UV conditions in January, November, and December allow for longer burn times of 30 minutes but still require caution. Visitors and residents should take appropriate precautions, such as wearing sunscreen, protective clothing, and sunglasses, especially during high UV months, to minimize the risk of skin damage.

Monthly Maximum UV Index for Nagano, Japan

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

The table above highlights how UV exposure in Nagano 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.

Nagano'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
Nagano	4	6	9	9	11	11	11	11	10	7	5	3
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