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San Jose, CA UV Index Today

Modelled for · GMT-7

What is the UV index in San Jose right now?

5 Moderate

EPA suggests shade around midday, a hat and sunglasses.

Today's peak is 7.2 (High) at about 1pm local time.

When is UV strongest in San Jose today?

UV in San Jose peaks at 7.2 (High) around 1pm local time (GMT-7). It stays at 6 or above — the high band — for 3 hours, roughly 12pm to 3pm. UV is 3 or above for 7 hours.

Local time, midnight to midnight. Bar colour is the EPA UV band, never restyled.

San Jose today, in numbers

Latitude
37.3°N — 77 of 121 from the north
Today's peak
7.2 (High) — 55 of 121 nationally
Peak arrives
1pm local (GMT-7)
At or above 6
3 hours, 12pm to 3pm
At or above 3
7 hours, 10am to 5pm

The window from 12pm to 3pm is the practical answer for San Jose today. Nationally today the spread runs 11.4 in Hilo (20°N) to 1.3 in Fargo (47°N). Why latitude and the clock decide this →

The Coast Range keeps the stratus offshore

The Santa Cruz Mountains do most of the work. San Jose sits on the floor of the Santa Clara Valley at about 82 feet with that ridge between it and the Pacific, and the summer stratus that holds Pacifica and Half Moon Bay under gray well into the morning usually thins or stops at the crest. The same barrier puts the South Bay in the range’s rain shadow. The practical effect is that a coastal reading and a San Jose reading can part company before noon on the same day: the coast loses its morning to cloud, the valley does not.

The calendar compounds it. This is a Mediterranean climate, so nearly all of the cloud and nearly all of the rain arrive between November and March, and May through September runs close to cloudless. Sun angle and cloud work in the same direction here rather than against each other, which is the opposite of the humid East, where the strongest sun months bring their own afternoon convection. The high-sun half of the year is also the half with almost nothing in the way.

The swing between the two ends is wide. The noon sun stands about 76 degrees above the horizon at the June solstice and about 29 degrees at the December solstice, so winter light is not only weaker but arriving through a much longer path of atmosphere.

Nearest metros we model

UV changes with latitude, not with a city boundary, so a neighbour a hundred miles north reads differently for a reason.

Oakland, CA 38 mi · 37.8°N peak 6.7 Stockton, CA 54 mi · 38.0°N peak 6.7 Sacramento, CA 88 mi · 38.6°N peak 6.8

What does San Jose’s UV index mean today?

5 is Moderate. EPA suggests shade around midday, a hat and sunglasses. Today San Jose also reaches High at its peak — a different band from the one it is in right now, which is why the hour matters as much as the day.

The scale is open-ended: 11 is where the named bands stop, not the maximum. All five bands, with the EPA guidance for each →

Modelled, not measured

The UV figures for San Jose are computed by the Copernicus atmosphere model, not read off an instrument here — unlike the AQI on our air-quality pages, which comes from a regulatory monitor. Cloud is where a UV model is weakest. What that means in practice →

Questions about UV in San Jose

What is the UV index in San Jose today?

5 right now (Moderate), peaking at 7.2 around 1pm local time. UV stays at 6 or above for 3 hours, from about 12pm to 3pm. This is a modelled value, not a ground measurement.

When is UV strongest in San Jose today?

Around 1pm local time (GMT-7), not at noon — solar noon drifts across a timezone and daylight saving moves it later on the clock.

Is this measured or modelled?

Modelled. The figures come from the Copernicus atmosphere model via Open-Meteo, unlike the AQI on our air-quality pages, which is read from an EPA regulatory monitor. Cloud cover is where a UV model is weakest.

San Jose air qualityThe AQI, from a regulatory monitor rather than a model UV across the USWhere San Jose sits against every metro we track

Updated