Air Quality in Ontario, California — Live
Live readings from PurpleAir sensors across Ontario — with free alerts the moment the air turns.
AQI 15 from 4 PurpleAir sensors · Holding steady · data from PurpleAir
As of , the air quality in Ontario, California is AQI 15 — Good and holding steady — with PM2.5 at 2.8 µg/m³, the median of 4 live PurpleAir sensors reading 1 to 26. 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 Ontario: weeds pollen is the strongest of the three at a moderate 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 Ontario and Upland, Montclair, Rancho Cucamonga, Chino. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Ontario
The sensors Canairy reads in Ontario agree right now — all 4 sit in the Good band, a 25-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 2.2 mi SSE | 26 | Good |
| 6.2 mi NW | 1 | Good |
| 6.4 mi NNW | 13 | Good |
| 7.2 mi SSW | 18 | Good |
Ontario is where a lot of the country's freight changes vehicles. Ontario International Airport is the eighth-busiest airport in the United States by cargo tonnage, moving 835,129 tons in 2024, and it runs around the clock as the West Coast hub for UPS Airlines, a major FedEx Express point, and a focus city for Amazon Air. Interstates 10 and 15 and State Route 60 all cross inside the city. Most of Southern California's air conversation is about ozone, and Ontario gets its share of that — but the traffic moving through is its own distinct story.
What Canairy does for Ontario
A clear verdict
Not just a number — a plain-English call for Ontario: 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 Ontario or across the country, on one screen.
What the air in Ontario is doing next
| When | AQI | Expected air quality | Main pollutant |
|---|---|---|---|
| Today | 87 | Moderate | ozone |
Forecast from EPA AirNow for the NW San Bernardino reporting area. Canairy watches the live sensors against it and tells you when the air actually crosses your threshold, rather than leaving you to check.
An airport that never really stops
Ontario International sits about two miles east of downtown, with two parallel runways of 12,197 and 10,200 feet. Unlike most Southern California airports it is permitted to operate twenty-four hours a day, with procedural restrictions between 10pm and 7am rather than a curfew, and comparatively few noise-abatement rules — residents in the cities west of the field have complained about it for years, and nighttime procedures send departing aircraft east instead. Cargo is still growing: more than 428,000 tons moved through in the first half of 2026, up 7.6 percent year over year.
The airport is only one piece of it. Ontario has one of the largest concentrations of warehouse space in the greater Los Angeles region, and the Ontario Ranch area in the south of the city — rezoned from farmland in 1999 — has absorbed much of the recent build-out. Warehouses of 100,000 square feet or more fall under the regional air district's warehouse rule, which requires operators to earn credit for emission-reducing actions or pay a mitigation fee.
Ontario still gets the regional smog on top of everything else
Being closer to Los Angeles does not exempt Ontario from the ozone problem — it just means the city sits mid-stream rather than against the mountain wall. The sea breeze carries coastal emissions east all day, sunlight converts them to ozone in transit, and the mountains ringing the basin keep the whole mass from escaping. San Bernardino County, which includes Ontario, ranked first in the nation for ozone in the American Lung Association's 2026 State of the Air report with 159.2 weighted unhealthy days, and seventh for year-round particle pollution.
This year has been worse than usual. The basin recorded 39 days above the federal ozone standard in the first five months of 2026, the highest count in more than a decade, which the air district attributed to an unusually early stretch of heat following California's warmest March on record. Ozone is close to invisible, so a hazy afternoon with no fire anywhere nearby is usually this rather than smoke.
Ontario air quality FAQ
What is the air quality in Ontario right now?
As of September 10, 2026 at 5:10 AM PDT, the air quality in Ontario, California is AQI 15 — Good — with PM2.5 at 2.8 µg/m³, the median of 4 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why is there smoke in Ontario today?
Ontario is rarely the fire; it is usually downwind or downslope of one. Fires in the San Bernardino National Forest and the Cajon Pass to the northeast put smoke into the valley — the Blue Cut Fire burned roughly 37,000 acres in the pass in August 2016 and triggered a valley-wide smoke advisory, and the Line Fire near Highland in September 2024 pushed monitors in that direction from moderate to hazardous. Smoke also arrives from the west when the winds shift. On a hot summer afternoon, brown haze with no fire nearby is usually ozone.
Does the airport affect the air where I live?
Ontario International operates around the clock, is the eighth-busiest US airport by cargo, and its traffic is still growing. Aircraft and the truck traffic that feeds them both emit particles and nitrogen oxides. What that means at a specific address depends on how far away you are and which way the wind is blowing, which no citywide number can tell you — that is what the sensor map below is for.
When is Ontario's air worst?
Ozone peaks on hot, still summer afternoons, and the air district issues advisories during heat waves. Fine particle pollution follows a different pattern — worse in cool stagnant weather, during wildfires, and around the Fourth of July.
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 4 curated PurpleAir sensors Canairy tracks in and around Ontario, 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
Go deeper
Air quality near Ontario
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