Air Quality in Fremont, California — Live
Live readings from PurpleAir sensors across Fremont — with free alerts the moment the air turns.
AQI 42 from 5 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in Fremont, California is AQI 42 — Good and falling — with PM2.5 at 7.6 µg/m³, the median of 5 live PurpleAir sensors reading 29 to 51. 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 Fremont: 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 Fremont and Union City, Newark, Hayward, Milpitas. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Fremont
The sensors Canairy reads in Fremont are 22 AQI points apart right now, from Good to Moderate, which is the whole reason one city-wide number can mislead you: the median describes air you may not be standing in.
| From city center | AQI | Category |
|---|---|---|
| 1.8 mi WSW | 43 | Good |
| 5.5 mi WNW | 42 | Good |
| 8.5 mi SSE | 41 | Good |
| 8.9 mi NW | 51 | Moderate |
| 9.8 mi SW | 29 | Good |
Fremont sits at the south end of the East Bay with the bay on one side and the Diablo Range on the other, and for most of the year that geography gives it good air. Across its whole monitoring network in 2023, the Bay Area Air Quality Management District recorded four days over the national 8-hour ozone standard and three days over the national 24-hour PM2.5 standard. What makes Fremont worth watching is not the annual average — it is the specific things sitting inside the city and just behind it: a car plant with a long enforcement history, I-880 and I-680 both running through town, and hills that have burned twice in recent memory.
What Canairy does for Fremont
A clear verdict
Not just a number — a plain-English call for Fremont: 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 Fremont or across the country, on one screen.
The factory on the east side of town
In June 2024 the Air District's Hearing Board ordered Tesla to fix ongoing air quality violations at its Fremont factory. The Air District said Tesla had racked up more than 112 notices of violation since 2019, nearly all of them traced to the plant's two paint shops, where the thermal oxidizer meant to destroy solvent vapours broke down repeatedly and was sometimes shut off while other equipment was being repaired. The pollutants at issue were precursor organic compounds — which react with nitrogen oxides in sunlight to form ozone — and toxic air contaminants.
The order gave Tesla roughly fifteen months to hire an outside engineering firm and produce a plan, then another six months to carry it out once the Hearing Board approved it. Separately, in February 2024 Tesla settled a hazardous waste case brought by California district attorneys, covering Fremont among other sites, for $1.5 million. One honest caveat: a neighbourhood sensor measures fine particles, not solvent vapours, so a paint shop release will not necessarily show up as a spike on the map below.
Fires start in the hills behind Fremont
The hills east of the city are the northern end of the Diablo Range, and they burn. The SCU Lightning Complex ignited in dry lightning on 16 August 2020 and burned 396,624 acres across Santa Clara, Alameda, Contra Costa, San Joaquin, Merced and Stanislaus counties before containment on 1 October — the fifth-largest wildfire in California's modern record, with 222 structures destroyed and no lives lost. Its Canyon Zone burned in Alameda and Santa Clara counties, in the range directly behind Fremont.
More recently, the Little Fire started just before 3pm on 21 July 2026 near Little Valley Road south of Pleasanton, reached 1,007 acres, and forced evacuations north of State Route 84 in Sunol — up Niles Canyon from Fremont's Niles district. The Air District warned that smoke would affect East Bay air quality, but said levels were not expected to exceed the national 24-hour standard, and no Spare the Air alert was issued. That is the more typical pattern here: a fire close enough to see and smell without a regionwide smoke event.
Most of the year, the bay does the work
The Air District describes Alameda County as split. In the western half, near the bay, ozone rarely exceeds health standards because the water moderates temperatures. In the eastern half, around the Livermore Valley, summer afternoons frequently approach triple digits and ozone runs the highest in the Bay Area. Fremont is firmly on the bayside half of that split, with Coyote Hills and the Don Edwards San Francisco Bay National Wildlife Refuge between the city and open water.
That is also why the sky can look far worse than the air actually is. On 9 September 2020, smoke from the North Complex and more than twenty other fires blocked out the sun across Northern California and held Bay Area skies orange all day — bridge and street lights stayed on, drivers were told to use headlights — while ground-level air quality read 90, in the moderate band. Your eyes and the sensor will not always agree, in either direction.
Fremont air quality FAQ
What is the air quality in Fremont right now?
As of September 10, 2026 at 5:10 AM PDT, the air quality in Fremont, California is AQI 42 — Good — with PM2.5 at 7.6 µg/m³, the median of 5 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why is there smoke in Fremont today?
Check the hills first. Fires in the Diablo Range east and south of the city, or up Niles Canyon toward Sunol, put visible smoke over Fremont without necessarily pushing the AQI far. The Little Fire near Sunol and Pleasanton in July 2026 burned over a thousand acres and the Air District expected East Bay smoke, but pollution was not forecast to exceed the national 24-hour standard. If there is no local fire in the news, it is more likely smoke drifting in from a larger fire elsewhere in Northern California, or on a cold winter evening, wood smoke from fireplaces settling in the flatlands.
Does the Tesla factory affect Fremont's air?
Regulators say it has. The Air District issued Tesla more than 112 notices of violation between 2019 and 2024 over uncontrolled releases from the factory's paint shops, and in June 2024 the Hearing Board ordered the company to fix the underlying equipment problems on a set timeline. The pollutants involved were ozone-forming organic compounds and toxic air contaminants — which are not the same thing as fine particles, and are not what a PurpleAir sensor reads. The sensors on this page are a good guide to smoke and general particulate conditions, not to solvent vapours.
When is Fremont's air usually at its worst?
Two windows. Late summer and early autumn, when Northern California fires are burning and smoke can arrive from hundreds of miles away — August and September 2020 were the extreme version of that. And cold, still winter nights, when wood smoke from fireplaces and stoves gets trapped near the ground; that is the season the Air District issues winter Spare the Air alerts and bans wood burning across the nine counties. The rest of the year, onshore air off the bay usually keeps things in the Good range.
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 Fremont, 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 Fremont
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