UV Index in Palo Alto, United States

Last updated: July 2, 2025

Understanding the UV Index is crucial for residents and visitors of Palo Alto, California, where the warm climate can lead to significant sun exposure. With UV levels regularly peaking between 9 and 10 during midday hours, awareness of these values is essential for preventing sunburn and protecting skin health. The typical Dfa climate in Palo Alto means that sunshine is abundant, yet it also poses risks for those who are unaware of the effects of prolonged exposure to UV rays. By keeping a close eye on the UV Index, you can enjoy the beautiful Californian weather while safeguarding your skin for years to come.

Hourly UV Index in Palo Alto

As the sun rises, the UV Index begins to climb, starting at a mild 1 at 7:00 AM. By 10:00 AM, it reaches a moderate 5, signaling the need for sun protection. The real peak occurs at 1:00 PM, with the index soaring to an intense 10—a critical point where sun safety is paramount. As the afternoon progresses, the UV levels gradually decline, dipping to 8 at 3:00 PM and settling back down to 2 by 6:00 PM. For anyone planning their day, it's essential to stay vigilant during the midday hours when the UV radiation is at its highest, ensuring skin is well-protected against potential damage.

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	3	moderate	30 min
10:00	5	moderate	30 min
11:00	7	high	25 min
12:00	9	very high	15 min
13:00	10	very high	15 min
14:00	9	very high	15 min
15:00	8	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 Palo Alto

Throughout the year, UV exposure varies significantly, peaking during late spring and summer months. High-risk months for UV exposure are April through September, where the UV Index frequently reaches levels classified as very high; particularly notable are May, June, and July, when it consistently hits a maximum of 10. Visitors and residents are advised to take precautions during these months, with burn times dramatically reduced to as little as 15 minutes. In contrast, January, February, and November present moderate UV levels, and December has a low index, making sun safety measures less critical during these months. To protect against skin damage, it is essential to wear sunscreen, seek shade, and wear protective clothing, especially between peak months of April and September.

Monthly Maximum UV Index for Palo Alto, United States

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

The table above highlights how UV exposure in Palo Alto 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.

Palo Alto'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
Palo Alto	3	5	6	9	10	10	10	9	8	6	4	2
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