Air Quality in San Diego, California — Live
Live readings from PurpleAir sensors across San Diego — with free alerts the moment smoke moves in.
AQI 54 from 5 PurpleAir sensors · Holding steady · data from PurpleAir
As of , the air quality in San Diego, California is AQI 54 — Moderate and holding steady — with PM2.5 at 10.9 µg/m³, the median of 5 live PurpleAir sensors reading 0 to 56. Canairy's verdict: Mostly clear.
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 San Diego: weeds pollen is the strongest of the three at a very 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 San Diego and Chula Vista, La Mesa, El Cajon, Coronado. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in San Diego
The sensors Canairy reads in San Diego are 56 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 |
|---|---|---|
| 1.2 mi N | 53 | Moderate |
| 1.4 mi SW | 0 | Good |
| 4.3 mi NNW | 56 | Moderate |
| 6.1 mi NNE | 55 | Moderate |
| 6.2 mi NE | 54 | Moderate |
San Diego trades on its ocean air, and for much of the year the reputation holds: the marine layer that rolls in off the Pacific keeps most days genuinely clean. But the picture is more complicated than the postcard. The region earned a failing grade for ozone in the American Lung Association's 2026 State of the Air report, ranking seventh worst in the country, and its Santa Ana wind season turns the coast into fire country. The 2003 Cedar Fire, the most destructive in county history at the time, burned all the way into the Scripps Ranch neighborhood of the city itself, and the 2007 Witch Creek Fire forced more than half a million residents to evacuate under heavy smoke.
What Canairy does for San Diego
A clear verdict
Not just a number — a plain-English call for San Diego: 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 San Diego or across the country, on one screen.
What the air in San Diego is doing next
| When | AQI | Expected air quality | Main pollutant |
|---|---|---|---|
| Today | 33 | Good | ozone |
| Tomorrow | 33 | Good | PM2.5 |
Forecast from EPA AirNow for the San Diego Coast 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 marine layer keeps the air clean until the wind turns around
San Diego's clean-air days are a gift of geography. Cool, moist air off the Pacific settles over the coast most mornings, the pattern locals know as May Gray and June Gloom, and onshore breezes generally push what pollution there is back out to sea. That same setup has a downside: a marine inversion traps cooler ocean air beneath a warmer layer above, and on stagnant days the lid holds tailpipe exhaust and other emissions close to the ground instead of letting them disperse.
The bigger swing comes with the Santa Ana winds. When high pressure builds over the Great Basin and pushes hot, dry desert air toward the coast, humidity crashes and fire danger spikes. A strong Santa Ana actually scours the air clean by blowing pollutants offshore, but a weak one does the opposite, carrying ozone-forming pollution south from the Los Angeles and South Coast air basin and driving San Diego's ozone up. It is the same wind pattern that makes autumn the most dangerous stretch of the year.
Fire season is a coastal problem here, not just a backcountry one
The Cedar Fire of October 2003 is the event locals still measure others against. Fanned by Santa Ana winds, it raced across more than 273,000 acres, killed 15 people, destroyed roughly 2,800 structures, and burned homes in Scripps Ranch, a neighborhood inside the city of San Diego rather than in the remote backcountry. Four years later the 2007 Witch Creek Fire burned close to 198,000 acres and forced more than 500,000 residents to evacuate.
The health record from those fires is clear. Studies of the San Diego wildfires found fine particulate matter pushed past the federal 24-hour standard and even some gases like carbon monoxide exceeded federal limits, and hospitals saw more patients arriving short of breath. Because Santa Ana winds can carry smoke straight to the coast, a fire burning miles inland can leave beach neighborhoods under unhealthy air within hours, which is exactly the kind of change worth catching early.
The border and the port carry their own year-round load
Away from fire season, San Diego's heaviest air burdens sit in its southern and bayfront communities. The San Ysidro port of entry is the busiest land crossing in the Western Hemisphere, with as many as 50,000 vehicles a day, and the county air district has flagged the border community for some of the worst diesel particulate pollution in the state. Researchers have also documented that gases rising off the polluted Tijuana River, including hydrogen sulfide, feed fine-particle formation in the surrounding valley.
Closer to downtown, Barrio Logan and neighboring National City sit against the Port of San Diego, its rail yards, and Interstate 5. Those neighborhoods rank in the 90th percentile statewide for diesel particulate matter, and children there face more than double the county's rate of asthma emergency-room visits. These are localized problems a citywide average hides, which is why the reading closest to your own block matters more than the number for the region as a whole.
San Diego air quality FAQ
What is the air quality in San Diego right now?
As of September 5, 2026 at 5:10 AM PDT, the air quality in San Diego, California is AQI 54 — Moderate — with PM2.5 at 10.9 µg/m³, the median of 5 live PurpleAir sensors. Sensitive groups may want to take it slower outside.
If San Diego is on the coast, why does it get bad air?
The ocean breeze keeps most days clean, but two things override it. On stagnant days a marine inversion traps tailpipe and other emissions close to the ground instead of letting them disperse, and San Diego earned a failing grade for ozone in the 2026 State of the Air report. Separately, a weak Santa Ana wind can carry ozone-forming pollution south from the Los Angeles air basin, while border-adjacent and portside neighborhoods carry heavy diesel loads year round.
Does wildfire smoke actually reach the San Diego coast?
Yes. The Santa Ana winds that drive the region's worst fires blow from the inland deserts toward the ocean, so smoke from a fire burning miles inland can settle over coastal neighborhoods within hours. The 2003 Cedar Fire burned into the Scripps Ranch neighborhood of the city itself, and the 2007 Witch Creek Fire forced more than 500,000 residents to evacuate. During those fires, fine particulate matter climbed past the federal health standard.
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 San Diego, 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 San Diego
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