Air Quality in Santa Clara, California — Live
Live readings from PurpleAir sensors across Santa Clara — with free alerts the moment the air turns.
AQI 17 from 5 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in Santa Clara, California is AQI 17 — Good and falling — with PM2.5 at 3.1 µg/m³, the median of 5 live PurpleAir sensors reading 7 to 31. Canairy's verdict: Breathe easy.
For scale, that PM2.5 reading is below the World Health Organization's 24-hour guideline of 15 µg/m³. The WHO figure is a daily average and this is a live reading, so read it as a sense of magnitude rather than a formal exceedance — a brief spike and a bad day are not the same thing. More on the WHO guidelines
Pollen today in Santa Clara: weeds pollen is the strongest of the three at a low level, from Google's pollen forecast. Canairy shows the tree, grass and weed forecast beside the air reading on every plan, including the free one.
Free to download · Live data from PurpleAir & public monitors
Live PurpleAir sensor map for Santa Clara and Sunnyvale, San Jose, Cupertino, Milpitas. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Santa Clara
The sensors Canairy reads in Santa Clara agree right now — all 5 sit in the Good band, a 24-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 2.5 mi WNW | 24 | Good |
| 5.4 mi W | 7 | Good |
| 6.1 mi SE | 31 | Good |
| 6.2 mi S | 8 | Good |
| 6.3 mi NW | 17 | Good |
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.
What Canairy does for Santa Clara
A clear verdict
Not just a number — a plain-English call for Santa Clara: open the windows, or keep them shut.
Smoke alerts
A push or text the moment the air crosses your threshold — and again when it clears.
A heads-up before it's bad
Trend alerts catch the air turning, so you can close up the house before the smoke settles in.
Every place you care about
Home, work, the kids' school — across Santa Clara or across the country, on one screen.
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?
As of September 10, 2026 at 5:09 AM PDT, the air quality in Santa Clara, California is AQI 17 — Good — with PM2.5 at 3.1 µg/m³, the median of 5 live PurpleAir sensors. Open the windows. Great for outdoor activity.
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 the AQI numbers mean
| AQI | Category | What it means for you |
|---|---|---|
| 0–50 | Good | Open the windows. Great for outdoor activity. |
| 51–100 | Moderate | Sensitive groups may want to take it slower outside. |
| 101–150 | Unhealthy for Sensitive Groups | Kids, elderly, and respiratory conditions stay closer to home. |
| 151–200 | Unhealthy | Skip outdoor exercise. Close windows. |
| 201–300 | Very Unhealthy | Limit time outside. N95 if you must go. |
| 301+ | Hazardous | Health emergency. Stay inside, run filtration if you have it. |
Canairy lets you tighten these bands if you’re more sensitive than the EPA default, so an alert can fire before the official category changes. How to read the Air Quality Index
Where these readings come from
The AQI at the top of this page is the median of the 5 curated PurpleAir sensors Canairy tracks in and around Santa Clara, with outliers set aside so that one sensor brought indoors — or parked beside a barbecue — cannot set the number for a whole city. Every sensor behind it is listed above with its distance and bearing from the city center. There is no black box here.
In the app, a place you save resolves the same way first. When no neighborhood sensor is reporting it falls back to the nearest EPA AirNow monitor, and anything modeled rather than measured is labelled a regional estimate rather than passed off as a sensor reading. How low-cost sensors compare to regulatory monitors
About Canairy
Canairy is free to download. The free plan covers one saved place with live readings, a plain-English verdict, and push alerts when the air crosses a threshold you choose. Paid plans add more places, faster refreshes, and SMS alerts. It is built by two parents in Sonoma County, California, who got tired of guessing whether it was safe to send the kids outside. Why we built it
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Air quality near Santa Clara
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