UV Index in Napa, United States

Last updated: June 2, 2025

Understanding the UV Index is crucial for residents and visitors in Napa, United States, where sunny days abound in the pleasant Csb climate. The UV Index measures the strength of ultraviolet radiation from the sun, helping us gauge the potential for skin damage, including sunburn and long-term health risks like skin cancer. With peak UV levels reaching as high as 11 around midday, awareness of these levels can significantly aid in sun safety and skin health. In Napa, knowing when to seek shade or apply sunscreen can make all the difference as you enjoy the beautiful outdoor lifestyle.

Hourly UV Index in Napa

As the sun rises, the UV Index begins its ascent, starting at a mild 1 at 07:00. By 08:00, it gently climbs to 2, but watch out as it rampages up to 4 by 09:00. The real intensity kicks in at 10:00, when the index hits a 6, and it reaches its peak of 10 at 12:00. The sun is relentless, pushing the index to 11 from 13:00 to 14:00, making this the most hazardous time of the day. Fortunately, the UV levels start to decline after 15:00, dropping back to 9, then dwindling to 4 by 17:00, and finally retreating to a safer 1 by 19:00. Ensure you take proper sun protection measures during the peak hours to safeguard your skin!

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	1	low	45 min
08:00	2	low	45 min
09:00	4	moderate	30 min
10:00	6	high	25 min
11:00	9	very high	15 min
12:00	10	very high	15 min
13:00	11	extreme	10 min
14:00	11	extreme	10 min
15:00	9	very high	15 min
16:00	6	high	25 min
17:00	4	moderate	30 min
18:00	2	low	45 min
19:00	1	low	45 min

Monthly UV Index Trends in Napa

Throughout the year, UV exposure varies significantly, with high-risk months typically occurring from March to September. During these months, particularly in April through July, the UV index reaches notably high levels, peaking at 11, which indicates extreme exposure risks and a quick burn time of just 10 minutes. As the seasons shift, visitors and residents should be particularly vigilant from May to August, when protective measures such as sunscreen, hats, and seeking shade are essential to prevent skin damage. In contrast, January, November, and December present a moderate UV index of 3-4, allowing for longer burn times of 30 minutes, though sunscreen should still be applied. Staying informed about these UV changes can help ensure safe outdoor activities year-round.

Monthly Maximum UV Index for Napa, United States

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

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

Napa's solar exposure compared to other cities in United States. Generated using Copernicus Atmosphere Monitoring Service information.
	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Chicago UVI	3	4	6	8	9	10	10	9	8	6	4	2
Brooklyn UVI	3	5	6	8	10	10	9	9	8	6	4	2
New York City UVI	3	5	6	8	10	10	9	9	8	6	4	2
Napa	3	5	7	9	10	11	11	10	9	6	4	3
Los Angeles UVI	4	6	8	9	10	11	11	10	10	7	5	4
Houston UVI	5	8	9	11	11	12	12	11	10	9	7	5