UV Index in Altadena, United States

Last updated: May 3, 2025

Being aware of the UV Index in Altadena, United States is crucial for safeguarding your skin from harmful UV radiation. Understanding the UV levels can help prevent sunburn and promote long-term skin health, especially during the peak hours of exposure when the index can reach as high as 11. With Altadena's mild Csb climate, residents and visitors alike should be mindful of the sun's intensity, particularly from late morning to early afternoon, when the risk of skin damage dramatically increases. Stay informed and protect yourself by checking the UV Index regularly, enjoying the sun safely!

Hourly UV Index in Altadena

As the sun rises, the UV Index begins steadily climbing, starting at a mere 1 at 7:00 AM. By 9:00 AM, it reaches a moderate 4, signaling more intense rays ahead. The peak arrives right at 12:00 PM, where the UV Index hits a sizzling 10, followed closely by a high of 11 at 1:00 PM—perfect times to seek shade and protect your skin. As the afternoon progresses, the numbers gently descend, dipping to 8 at 3:00 PM and eventually falling back to 1 by 7:00 PM. This hourly data paints a clear picture: mid-day offers the strongest sun exposure, making sun safety paramount during those crucial hours. Enjoy the sun, but stay protected!

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	10	very high	15 min
15:00	8	very high	15 min
16:00	5	moderate	30 min
17:00	3	moderate	30 min
18:00	1	low	45 min
19:00	1	low	45 min

Monthly UV Index Trends in Altadena

Throughout the year, the UV Index demonstrates notable seasonal changes, with the most intense exposure occurring from April to August. During these months, the UV Index reaches extreme levels (10-12), significantly reducing the burn time to just 10 minutes. March and September also pose risks with very high levels (8-10), allowing for a burn time of only 15 minutes. Consequently, February and October present high levels (6-7), where protective measures are still advised with adjusted burn times of 25 minutes. Residents and visitors should exercise caution and protect their skin, especially during the high-risk months of April through August, by using sunscreen, wearing protective clothing, and limiting sun exposure during peak hours.

Monthly Maximum UV Index for Altadena, United States

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

The table above highlights how UV exposure in Altadena 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.

Altadena'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
Los Angeles UVI	4	6	8	9	10	11	11	10	10	7	5	4
Altadena	4	6	8	10	11	11	12	11	10	7	5	4
Houston UVI	5	8	9	11	11	12	12	11	10	9	7	5