Air Quality in Santa Clara, California — Live

Live readings from PurpleAir sensors across Santa Clara — with free alerts the moment the air turns.

Live Santa Clara AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Santa Clara and Sunnyvale, San Jose, Cupertino, Milpitas.

Santa Clara is eighteen square miles wrapped almost entirely by San Jose, and for most of the year its air behaves like the rest of the north valley: good, with a breeze off the bay in the afternoon and the occasional smoky week in late summer. What sets it apart from its neighbours is what the city itself owns and hosts. Santa Clara runs its own electric utility, generates part of its power from a gas plant inside the city limits, and has become the densest concentration of data centres in California, each with banks of diesel engines standing by.

Canairy watches the sensors around your home, your kids' school, and everywhere else you care about, and tells you in plain English when the air changes enough to matter.

Santa Clara makes its own electricity, inside the city limits

Almost every Bay Area city buys its power from PG&E. Santa Clara does not. The city has owned and run its own utility, Silicon Valley Power, for well over a century, and part of what it sells it generates here. The Donald Von Raesfeld Power Plant at 850 Duane Avenue is a combined-cycle natural gas plant, two 50-megawatt combustion turbines feeding a 22-megawatt steam turbine for 147 megawatts of peak output, commissioned in March 2005. It holds a Title V permit from the Bay Area Air Quality Management District.

Be honest about what that means for the number at the top of this page. A permitted combined-cycle gas plant is mainly a source of nitrogen oxides, which react with sunlight to help form ozone on hot afternoons. It is not a large source of fine particles, and fine particles are what the sensors on this map read. If you want the plant's own record, its Air District permit and its annual reports to the California Energy Commission are public documents.

Fifty-five data centres, and the diesel that backs them up

Santa Clara has become the data centre capital of Silicon Valley, largely because Silicon Valley Power's rates are low. As of September 2025 the city counted 55 data centres with three more in the pipeline. They buy 60 per cent of the power the utility sells, around 700 megawatts today, with projections toward 1,300. Data centre revenue is now the third-largest source in the city's general fund.

Facilities like that keep large diesel generators for backup, and those engines need an Air District permit before they can be installed. Statewide, of the thirteen California data centres approved for the state's Small Power Plant Exemption, eleven are in Santa Clara and San Jose, some of them near homes and schools. In normal operation these engines run for periodic testing rather than continuously, so the effect on a neighbourhood is episodic rather than constant, which is exactly the sort of thing a local sensor catches and a monthly average buries.

Three freeways cross this city

For a city this compact, Santa Clara carries a lot of through traffic. US 101 runs across its northern half, State Route 237 tracks the bay edge toward Milpitas, Interstate 880 cuts down its eastern side, and Lawrence Expressway runs north to south through the west of the city. Between them, most Santa Clara addresses are within a mile of a major road.

That matters more at street level than a citywide figure suggests. Traffic pollution falls off sharply with distance from the roadway, so a house two blocks off Lawrence Expressway and a house backing onto it can genuinely be in different air during the morning and evening peaks. Picking the sensor nearest your own block, rather than the city average, is the whole point of a dense network.

Santa Clara air quality FAQ

What is the air quality in Santa Clara right now?

This page shows the current AQI for Santa Clara, calculated from PurpleAir sensors across the city and updated continuously. The map below shows every live sensor behind that number, so you can check the reading closest to your own street rather than a single figure for the whole city.

Why is there smoke in Santa Clara today?

Santa Clara has no wildland of its own, so visible smoke here has drifted in from somewhere else, usually a fire in the Diablo Range to the east, the Santa Cruz Mountains to the west, or a larger fire much further north in California. On a cold, still winter evening a haze is more likely to be wood smoke from fireplaces settling near the ground. The live reading on this page will tell you inside a few minutes whether it is worth closing the windows.

Do the data centres affect Santa Clara's air quality?

The buildings themselves do not emit much; the question is their backup diesel generators, which need an Air District permit and which run mainly for periodic testing. Eleven of the thirteen California data centres approved for the state's Small Power Plant Exemption are in Santa Clara and San Jose, some near homes and schools. Because generator testing is short and local, the honest answer is that a sensor near your own block is a far better guide than any citywide figure.

Does the city's power plant show up on the sensors?

Not really, and it is worth knowing why. The Donald Von Raesfeld plant on Duane Avenue is a 147-megawatt combined-cycle natural gas plant that Silicon Valley Power has run since 2005 under an Air District Title V permit. Gas turbines are principally a nitrogen oxide source, and nitrogen oxides feed ozone rather than fine particles. The sensors on this page measure fine particles, so they are a good guide to smoke and haze and a poor one to what the plant emits.

What AQI level is unhealthy?

Under the US EPA scale, AQI 0–50 is Good and 51–100 is Moderate. From 101 the air is Unhealthy for Sensitive Groups — kids, older adults, and people with asthma or heart conditions — and above 150 it's Unhealthy for everyone. Canairy translates these numbers into a plain-English verdict, like whether to close the windows or move a workout indoors.

Is Canairy free?

Yes. The Canairy app is free to download and includes live air quality for all your saved places, plain-English verdicts, and free push alerts when the air crosses your threshold. A paid plan adds extras like SMS text alerts.

Get Canairy free on Google Play.