UV Index in Yorii, Japan

Last updated: August 1, 2025

Staying informed about the UV Index in Yorii, Japan, is crucial for safeguarding your skin and overall health. Understanding UV levels helps you take proactive measures against sunburn and long-term skin damage, particularly as the UV Index can reach extreme values of 11 during midday hours. With Yorii's humid subtropical climate (Cfa), the potential for high UV exposure is significant, especially in spring and summer when outdoor activities are at their peak. By being aware of the daily UV Index, you can enjoy the beautiful outdoors while protecting your skin from harmful rays.

Hourly UV Index in Yorii

The UV Index throughout the day presents a dynamic picture of sun exposure. As early as 7:00 AM, the index starts at a mild 2, ramping up to a moderate 4 by 8:00 AM. The sun's intensity peaks around 11:00 AM and 12:00 PM with a striking 11, marking the height of caution for outdoor activities. As we move into the afternoon, the index gradually declines, dropping to 8 by 2:00 PM and further to 5 by 3:00 PM. The evening brings relief, with the UV Index decreasing to a 1 by 5:00 PM and finally hitting 0 by 7:00 PM. It’s clear that the midday hours pose the greatest risk, so sun safety measures are essential during those peak times.

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	6	high	25 min
10:00	9	very high	15 min
11:00	10	very high	15 min
12:00	11	extreme	10 min
13:00	10	very high	15 min
14:00	7	high	25 min
15:00	5	moderate	30 min
16:00	3	moderate	30 min
17:00	1	low	45 min
18:00	1	low	45 min
19:00	0	low	45 min

Monthly UV Index Trends in Yorii

Throughout the year, UV exposure varies significantly, necessitating careful planning for both visitors and residents. The high-risk months for UV radiation are from March to August, with the UV Index peaking at an extreme level of 11 during May, June, July, and August, where the recommended burn time is just 10 minutes. In contrast, January, November, and December present a moderate UV Index of 3 to 5, allowing for longer exposure times of 30 minutes. To ensure safety, it is crucial to wear sunscreen, protective clothing, and sunglasses during the high-risk months, and to seek shade whenever possible to minimize skin damage from excessive UV radiation.

Monthly Maximum UV Index for Yorii, Japan

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

The table above highlights how UV exposure in Yorii 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.

Yorii'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
Yorii	3	5	8	9	11	11	11	11	9	7	5	3
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