UV Index in Altadena, United States

Last updated: July 2, 2025

In Altadena, United States, awareness of the UV Index is crucial for protecting your skin and overall health. With its Csb climate characterized by warm summers, understanding UV levels helps residents and visitors alike minimize sunburn risk and safeguard against long-term skin damage. The UV Index can reach a peak of 12 at noon, indicating a high level of solar intensity that requires proactive measures for sun protection. Being informed about daily UV exposure not only ensures better skin care but also enhances your outdoor enjoyment in this beautiful region.

Hourly UV Index in Altadena

The UV Index throughout the day showcases a dynamic pattern, beginning with a mild level of 1 at 7:00 AM and gradually climbing to a striking peak of 12 by 1:00 PM. This midday maximum indicates a high risk for unprotected skin, urging caution as UV radiation is particularly intense. As the afternoon unfolds, the index gradually decreases, dropping to 9 at 3:00 PM, and continues to decline until it returns to a safe 1 by 7:00 PM. Between 11:00 AM and 2:00 PM, when the index hovers around 11 to 12, it's essential to seek shade or apply sunscreen for optimal protection. Overall, this UVI data emphasizes the importance of being 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	1	low	45 min
08:00	2	low	45 min
09:00	4	moderate	30 min
10:00	7	high	25 min
11:00	9	very high	15 min
12:00	11	extreme	10 min
13:00	12	extreme	10 min
14:00	11	extreme	10 min
15:00	9	very high	15 min
16:00	6	high	25 min
17:00	3	moderate	30 min
18:00	2	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