Air Quality in Pasadena, California — Live
Live readings from PurpleAir sensors across Pasadena — with free alerts the moment the air turns.
AQI 38 from 4 PurpleAir sensors · Trending up · data from PurpleAir
As of , the air quality in Pasadena, California is AQI 38 — Good and rising — with PM2.5 at 6.9 µg/m³, the median of 4 live PurpleAir sensors reading 20 to 52. 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 Pasadena: 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 Pasadena and Altadena, Sierra Madre, South Pasadena, San Marino, Arcadia, La Cañada Flintridge. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Pasadena
The sensors Canairy reads in Pasadena are 32 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 |
|---|---|---|
| 2.6 mi SSE | 47 | Good |
| 3.6 mi WNW | 20 | Good |
| 3.9 mi WSW | 52 | Moderate |
| 4.1 mi ENE | 30 | Good |
Pasadena sits at 863 feet at the foot of the San Gabriel Mountains, about 10 miles northeast of downtown Los Angeles, with the Angeles National Forest greenbelt above it, the Arroyo Seco cutting through it and the San Rafael Hills on its western side. Those mountains give the city about 20 inches of rain a year, roughly six more than Los Angeles gets, because air rising over the range drops its water here. The same wall that squeezes out the rain also pens in the air, and it is why Pasadena has been on the wrong end of two very different air problems — the photochemical smog that was first explained in a laboratory in this city, and, in January 2025, the smoke and ash of a fire that burned right at its northern edge.
What Canairy does for Pasadena
A clear verdict
Not just a number — a plain-English call for Pasadena: 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 Pasadena or across the country, on one screen.
What the air in Pasadena is doing next
| When | AQI | Expected air quality | Main pollutant |
|---|---|---|---|
| Today | 67 | Moderate | ozone |
Forecast from EPA AirNow for the W San Gabriel Vly 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.
The Eaton Fire and the weeks after it
The Eaton Fire started at about 6:18 p.m. on 7 January 2025 in Eaton Canyon, during a Santa Ana wind event that produced gusts of 100 mph at Mount Lukens in the eastern San Gabriels. It burned 14,021 acres before it was fully contained on 31 January, 24 days later. Nineteen people were killed. As of 21 January, 9,418 structures had been destroyed and a further 1,071 damaged, most of them in Altadena immediately north of the city, with portions of Pasadena itself also destroyed. In September 2025 the US Department of Justice sued Southern California Edison, attributing the fire to faulty power lines.
For anyone downwind, the numbers that mattered were the ones on an air monitor. Regional air quality index readings passed 200 into the Very Unhealthy category, and California Air Resources Board data recorded a one-hour peak of 483.7 micrograms per cubic metre of PM2.5 at the Los Angeles-North Main Street station. Because the fire consumed houses rather than only brush, the smoke carried what houses are made of: the CDC later reported a 110-fold increase in air lead levels during the fires, from the combustion of painted surfaces and pipes in pre-1978 structures. Los Angeles County Public Health extended its smoke advisory through 5 p.m. on Saturday 11 January, naming the area of Altadena and Pasadena, and Pasadena Unified School District closed through Friday 10 January.
What the testing found afterwards
The follow-up is worth knowing, because the honest version is more reassuring than the rumour version. Pasadena Public Health conducted environmental testing at nine city facilities, and South Coast AQMD ran mobile air monitoring across the area on 31 January 2025. No asbestos was detected at the city facilities. Lead measurements fell below the US EPA's Dust Lead Action Level of 5 micrograms per square foot. The mobile monitoring found no elevated levels of heavy metals such as lead or arsenic, or of benzene, with results remaining within background levels and below both national standards and state health thresholds. Elevated methane was detected in Altadena, possibly indicating gas leaks.
On the strength of that data the city amended rather than ended its local health emergency declaration, with acting health officer Parveen Kaur explaining that the department was updating it to reflect the priorities posed by current conditions — reducing contaminant exposure, safe removal of toxic substances from private property, and access to recovery funding. Pasadena Public Health's advisory of 17 January had already set out what to do indoors, and it is still a sensible template for any smoke event: wear a NIOSH-approved N95 or P100 respirator while cleaning your home, even if you were not directly affected; run a portable air cleaner with both a HEPA filter and an activated carbon filter, since the HEPA element removes 99.97 percent of the fine particles that reach deepest into the lungs; and fit MERV 11 or 12 filters in the furnace or HVAC, changing them monthly until the smell is gone.
The older problem, and why the mountains matter
Long before the fire, Pasadena had a claim on air quality history. Arie Haagen-Smit, a professor at Caltech here, began investigating air pollution in 1948 after Southern Californians started suffering stinging eyes and respiratory irritation and crops in the basin began showing damage. He showed that the haze was not simple soot but the product of a photochemical reaction, with sunlight acting on unburned hydrocarbons, ozone and nitrogen oxides from vehicle exhaust and industrial fuel combustion. By the mid-1950s the link between cars and Los Angeles smog was broadly accepted, and in 1968 Haagen-Smit was appointed the first chairman of the California Air Resources Board.
That chemistry has not gone away, and Pasadena's geography still favours it. Ozone is a hot-afternoon pollutant, not a cold-morning one, because it needs strong sunlight to form, and the San Gabriel Mountains at the city's back hold the air in place long enough for the reaction to run. It is the reason a day can look perfectly clear and still be a bad day to run the Rose Bowl loop or leave a school field session outdoors — and the reason a live number beats a look out of the window.
Pasadena air quality FAQ
What is the air quality in Pasadena right now?
As of September 11, 2026 at 5:10 AM PDT, the air quality in Pasadena, California is AQI 38 — Good — with PM2.5 at 6.9 µg/m³, the median of 4 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why is there smoke in Pasadena today?
Most often a wildfire in the San Gabriel Mountains or the Angeles National Forest directly above the city, or one further out in the basin whose smoke has drifted in and settled against the range. The clearest recent example was the Eaton Fire, which started on the evening of 7 January 2025 in Eaton Canyon, burned 14,021 acres before containment on 31 January, and put Altadena and Pasadena under a Los Angeles County smoke advisory that was extended through 5 p.m. on 11 January. Regional AQI readings passed 200 during that week. Smoke is not the only cause of a bad number here, though — ozone builds on hot, sunny afternoons with no fire involved at all.
Is ash from the Eaton Fire still a health concern in Pasadena?
Pasadena Public Health warned on 17 January 2025 that ash can irritate skin, eyes, nose and throat, make breathing difficult and aggravate asthma, and advised everyone to wear an N95 or P100 mask when cleaning their home, whether or not they were directly hit by the fire. The testing that followed was largely reassuring: nine city facilities showed no asbestos and lead below the EPA's Dust Lead Action Level of 5 micrograms per square foot, and South Coast AQMD mobile air monitoring on 31 January found no elevated heavy metals or benzene, with results within background levels. The city amended its local health emergency rather than ending it, keeping the focus on safe removal of contaminants from private property.
Why does Pasadena have a reputation for smog?
Because the science of Los Angeles smog was worked out here. Arie Haagen-Smit at Caltech began his air pollution research in 1948 and demonstrated that the haze came from a photochemical reaction between unburned hydrocarbons, ozone and nitrogen oxides from car exhaust and industrial combustion, driven by sunlight; he went on to become the first chairman of the California Air Resources Board in 1968. The conditions that made Pasadena a good place to study the problem have not changed. Strong sun, a large basin full of traffic, and the San Gabriel Mountains standing directly behind the city to hold the air in place.
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 Pasadena, 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 Pasadena
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