What is the UV index in San Francisco today?

See today's UV index for San Francisco hour by hour above. The UV index is highest around solar noon and depends on the season, the weather and how high the sun rises above the horizon.

When is the UV index highest?

The UV index peaks around solar noon, typically between 12:00 and 15:00, when the sun is highest in the sky. About two-thirds of the day’s total UV falls between 10:00 and 16:00.

When should you use sunscreen?

The WHO recommends sun protection whenever the UV index is 3 or higher. Use sunscreen of at least SPF 30, seek shade around midday, and wear sunglasses and a hat when UV is high.

Daylight Hours › UV Index › San Francisco

UV Index in San Francisco Today

November 13, 2026 · San Francisco, USA

864,816 people

See today's UV index in San Francisco hour by hour below. The UV index shows how strong the sun's ultraviolet radiation is — the higher the number, the faster skin can burn. Values are calculated for San Francisco's coordinates and updated daily.

UV now · 05:00

0Low

No protection needed

Peak today1at 14:00

Protect yourselfNot neededUV stays below 3

Hour by hour

Clouds cut the peak by ~19%

Clear sky

Remember today

Safe to be outside unprotected

Daylight: sunrise 06:49 – sunset 17:01

Tomorrow: UV 3 at its peak around 12:00

Calculate for San Francisco Use my location

The UV index in San Francisco peaks at 1 (low) around 14:00 today. The index stays below 3 all day, so no particular sun protection is needed. Cloud cover is damping the peak by roughly 19% compared with a clear sky. Tomorrow the index is forecast to peak at 3 around 12:00.

UV index in San Francisco hour by hour

Time	UV index	Level
06:00	0	Low
07:00	0.1	Low
08:00	0.2	Low
09:00	0.2	Low
10:00	0.2	Low
11:00	0.3	Low
12:00	0.5	Low
13:00	1.2	Low
14:00	1.3	Low
15:00	0.6	Low
16:00	0.2	Low
17:00	0	Low
18:00	0	Low

UV index in San Francisco

San Francisco lies at 38°N. The midday sun reaches 34.2° above the horizon in San Francisco today, against a yearly ceiling of 75.7°. Elevation is what sets the ceiling for UV, and over San Francisco it is high enough for the index to reach very high values through the summer months. San Francisco is on the coast, where water and sand reflect UV back up at you and the sea breeze hides the heat that would otherwise send you into the shade.

What is the UV index?

The UV index is an international scale describing the strength of the sun's ultraviolet radiation at ground level. It starts at 0 and is effectively open-ended — at mid-latitudes it rarely exceeds 8, while in the tropics and high in the mountains it can pass 11. The higher the number, the less time it takes to get sunburnt.

The UV index depends mainly on how high the sun is in the sky. That is why it peaks around solar noon and is greatest in summer near the longest day of the year. Clouds, ozone, altitude and reflection from snow or water also affect the value.

The WHO UV scale

UV index	Level	Recommendation
0–2	Low	No special protection needed.
3–5	Moderate	Use sunscreen (SPF 30+), seek shade around midday.
6–7	High	Sunscreen, hat and sunglasses. Avoid the sun 12:00–15:00.
8–10	Very high	Extra protection. Limit midday sun exposure.
11+	Extreme	Avoid the sun at midday. Full protection required.

See also sunrise, sunset and daylight hours in San Francisco.