Air Quality in Napa, California — Live
Live readings from PurpleAir sensors across Napa — with free alerts the moment smoke moves in.
AQI 30 from 5 PurpleAir sensors · Holding steady · data from PurpleAir
As of , the air quality in Napa, California is AQI 30 — Good and holding steady — with PM2.5 at 5.4 µg/m³, the median of 5 live PurpleAir sensors reading 7 to 34. 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 Napa: 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 Napa and Yountville, St. Helena, American Canyon, Calistoga. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Napa
The sensors Canairy reads in Napa agree right now — all 5 sit in the Good band, a 27-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 1.3 mi SSW | 7 | Good |
| 2.3 mi WNW | 23 | Good |
| 2.9 mi NW | 30 | Good |
| 4.5 mi SW | 34 | Good |
| 4.7 mi NW | 30 | Good |
Most days in Napa the air is clean, helped by the marine breeze that pulls in off San Pablo Bay on summer afternoons. The trouble comes in two forms: wildfire smoke in late summer and fall, and the fine particles that settle into the valley on cold, still winter nights when the mountains hold the air in place.
What Canairy does for Napa
A clear verdict
Not just a number — a plain-English call for Napa: 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 Napa or across the country, on one screen.
What the air in Napa is doing next
| When | AQI | Expected air quality | Main pollutant |
|---|---|---|---|
| Today | 36 | Good | ozone |
| Tomorrow | 37 | Good | ozone |
| Monday | 38 | Good | ozone |
| Tuesday | — | Good | ozone |
| Wednesday | — | Good | ozone |
Forecast from EPA AirNow for the Napa 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 valley holds the air in place
Napa sits in a valley pinched between the Mayacamas Mountains to the west and the Vaca Mountains to the east. Those ridges, averaging around 2,000 feet, block most of the prevailing northwesterly winds, so much of the county is wind-sheltered and the air moves slowly. Nearly half the time the wind is under 4 miles per hour, which is calm enough to let fine particles build up rather than blow through.
That same geography is what makes smoke linger here. When a fire is burning or a winter inversion settles in, there is little wind to clear the valley, and pollutants can be recirculated by the upslope and downslope flows off the surrounding hills. The saving grace in summer is the upvalley breeze that develops on warm afternoons, drawing cleaner air in from San Pablo Bay to the south.
Wildfire smoke is the reason for the failing grade
The American Lung Association gives Napa County a failing F for short-term particle pollution, and it is wildfire smoke that earns it. The Atlas Fire started on Atlas Peak Road just north of the city on the night of October 8, 2017, burned more than 51,000 acres, and forced an evacuation advisory for parts of Napa itself as part of the larger North Bay firestorm alongside the Tubbs and Nuns fires. In 2018, smoke from the Camp Fire in Butte County drifted down and fouled the valley's air for days even though the fire was more than a hundred miles away.
The Glass Fire in September 2020 was closer still, igniting near Deer Park in the hills above the valley and pushing air quality index readings to around 170 as tens of thousands of people evacuated. On the worst days county officials told everyone to stay indoors. This is the pattern Napa has learned to live with: for a few weeks most years, late summer and fall can turn the sky brown and the air genuinely dangerous.
Winter brings a quieter kind of pollution
Wildfire is not the only source. Napa gets some of the coldest nights in the Bay Area because it sits far enough north to miss much of the bay's moderating warmth, and cold nights mean more wood fires. Smoke from home fireplaces and stoves is a real contributor to the valley's winter PM2.5, and on a still, cold evening it has nowhere to go.
On top of that, winter easterly winds can carry fine-particle-laden air out of the Central Valley, through the Carquinez Strait, and up into southern Napa County. Between the local wood smoke and this imported haze, the valley's cleanest-looking winter days can still carry a load of particles you would not notice without a sensor. Ozone, by contrast, is rarely a problem here, and the county earns a solid B for it.
Napa air quality FAQ
What is the air quality in Napa right now?
As of September 5, 2026 at 5:09 AM PDT, the air quality in Napa, California is AQI 30 — Good — with PM2.5 at 5.4 µg/m³, the median of 5 live PurpleAir sensors. Open the windows. Great for outdoor activity.
What causes Napa's worst air-quality days?
Two things. In late summer and fall it is wildfire smoke, which the surrounding mountains and calm winds tend to trap in the valley. In winter it is fine particles from wood-burning fireplaces on cold, still nights, sometimes added to by haze carried in from the Central Valley on easterly winds. Ground-level ozone, the summer smog problem in many California cities, is rarely an issue in Napa.
Which wildfires had the biggest effect on Napa's air?
The Atlas Fire in October 2017 started on Atlas Peak Road just north of the city, burned more than 51,000 acres, and prompted an evacuation advisory for parts of Napa. The Glass Fire in September 2020 ignited near Deer Park above the valley and pushed the air quality index to around 170, with officials advising everyone to stay indoors. Smoke from the 2018 Camp Fire also reached the valley from well over a hundred miles away.
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 Napa, 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 Napa
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