Air Quality in San Bernardino, California — Live

Live readings from PurpleAir sensors across San Bernardino — with free alerts the moment the air turns.

Live San Bernardino AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering San Bernardino and Highland, Rialto, Colton, Redlands.

San Bernardino sits at the closed end of a valley. The San Bernardino Mountains rise straight up on the north side of town, the San Gabriels close it off to the west, and the sea breeze off the Pacific pushes Los Angeles-area exhaust inland all day until it stacks up here against the rock. Sunlight cooks that mix into ozone on the way over, which is why smog is worst inland and mildest at the coast — the opposite of what most people assume. In the American Lung Association's 2026 State of the Air, San Bernardino County ranked first in the country for ozone, with a weighted average of 159.2 unhealthy ozone days a year. The same mountains that trap the smog also hold the fuel.

Canairy watches the sensors around your home, your kids' school, and everywhere else you care about, and tells you in plain English when the air changes enough to matter.

Why the smog gets worse the farther east you go

It runs against intuition, but the coast has the cleanest air in the basin and San Bernardino has the dirtiest. Ozone is not emitted directly — it forms when nitrogen oxides and volatile organic compounds react in sunlight. Emissions produced along the coast take hours to cook, and by the time the reaction is finished the sea breeze has carried the whole mass thirty or sixty miles inland. The mountains ringing the basin then stop it. The air district's own analysis puts the greatest number of federal 8-hour ozone exceedances in the eastern San Bernardino Valley, and notes that exceedances are lowest at the coast for exactly this reason.

That is why bad air days here tend to peak on hot, still summer afternoons rather than in the morning rush. The basin is classified extreme nonattainment for the 2015 federal ozone standard. The first five months of 2026 produced 39 days over that standard basin-wide, the worst start to a year in more than a decade, which air district staff attributed to an unusually early run of heat after California's warmest March on record.

Smoke here comes down off the mountains

The San Bernardino National Forest starts at the city's northern edge, and the Cajon Pass cuts through the range just northwest of town. When something burns up there, the smoke settles into the valley below. The Old Fire started near Old Waterman Canyon Road on October 25, 2003, burned for nine days, took 91,281 acres and 993 homes, killed six people, and forced evacuations in San Bernardino and Highland along with Crestline, Running Springs and Lake Arrowhead.

It has kept happening. The Line Fire started September 5, 2024 near Highland and grew past 20,000 acres; monitors around it read anywhere from moderate to hazardous, with the worst readings up the hill in Highland, Running Springs and Lake Arrowhead. In August 2016 the Blue Cut Fire burned roughly 37,000 acres in the Cajon Pass and forced more than 82,000 people out. Smoke also arrives from much farther away — when the Eaton Fire burned in Altadena in January 2025, sixty miles west, the smoke advisory still reached east into the Inland Empire as the winds shifted.

The freight corridor on the west side of town

San Bernardino is a goods-movement hub as well as a valley, and that shows up in the local air separately from the regional smog. The state selected San Bernardino and Muscoy in September 2018 as one of the first ten AB 617 communities in California — a 31-square-mile area of about 152,000 people whose maximum CalEnviroScreen score falls in the top one percent statewide, meaning some of the most burdened neighborhoods in the state. The community emissions reduction plan was adopted in 2019 and is still reported on annually.

Two things drive that designation. The BNSF intermodal railyard has been the subject of a formal California Air Resources Board health risk assessment, one of seventeen major railyard assessments the board completed in the late 2000s. And at San Bernardino International Airport, a 658,500-square-foot air cargo facility now operating as an Amazon Air hub was approved over a legal challenge from the California Attorney General, who argued the environmental review understated truck and jet emissions.

San Bernardino air quality FAQ

Why is there smoke in San Bernardino today?

The usual answer is a fire in the San Bernardino Mountains or the Cajon Pass, just north and northwest of the city, with the smoke settling into the valley below. That was the pattern with the Old Fire in 2003, the Blue Cut Fire in 2016, and the Line Fire near Highland in September 2024. Less often it is smoke that has drifted east from Los Angeles County. And on a hot summer afternoon, brown haze with no fire nearby is often ozone rather than smoke — it is essentially invisible, so the live reading is a better guide than the look of the sky.

What is the air quality in San Bernardino right now?

This page shows the current AQI for San Bernardino, calculated from PurpleAir sensors across the city and updated continuously. The map below shows every live sensor, so you can check the reading closest to your own neighborhood.

Why does San Bernardino County keep ranking worst in the country for smog?

Geography plus being downwind. The sea breeze pushes Los Angeles-area emissions inland every day, sunlight turns them into ozone en route, and the San Bernardino and San Gabriel Mountains stop the whole mass from moving any farther. In the American Lung Association's 2026 State of the Air report, San Bernardino County ranked first in the nation for ozone with 159.2 weighted unhealthy days — the twenty-sixth consecutive year the region has topped the national list.

When is the air worst here?

Ozone is a summer, afternoon problem — it needs heat and sunlight, and it builds through the day. Particle pollution runs on a different clock: it spikes during wildfires whenever they happen, and around the Fourth of July. Smoke events are most likely from late summer into fall, when the brush in the national forest is driest and Santa Ana winds are running through the Cajon Pass.

What AQI level is unhealthy?

Under the US EPA scale, AQI 0–50 is Good and 51–100 is Moderate. From 101 the air is Unhealthy for Sensitive Groups — kids, older adults, and people with asthma or heart conditions — and above 150 it's Unhealthy for everyone. Canairy translates these numbers into a plain-English verdict, like whether to close the windows or move a workout indoors.

Is Canairy free?

Yes. The Canairy app is free to download and includes live air quality for all your saved places, plain-English verdicts, and free push alerts when the air crosses your threshold. A paid plan adds extras like SMS text alerts.

Get Canairy free on Google Play.