Air Quality in Eureka, California — Live
Live readings from PurpleAir sensors across Eureka — with free alerts the moment smoke moves in.
AQI 15 from 5 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in Eureka, California is AQI 15 — Good and falling — with PM2.5 at 2.7 µg/m³, the median of 5 live PurpleAir sensors reading 9 to 57. 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 Eureka: grass 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 Eureka and Arcata, Fortuna, McKinleyville, Ferndale. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Eureka
The sensors Canairy reads in Eureka are 48 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 |
|---|---|---|
| 1.9 mi SSW | 19 | Good |
| 3.0 mi N | 57 | Moderate |
| 4.4 mi S | 11 | Good |
| 4.9 mi S | 9 | Good |
| 6.0 mi NE | 23 | Good |
For most of the year Eureka has some of the cleanest air in California. The town sits right on Humboldt Bay in the coastal fog belt, where a steady marine layer and northwesterly winds off the Pacific keep particulate levels low. The two things that change that are wildfire smoke drifting down from the interior in late summer and wood-stove smoke settling under winter inversions.
What Canairy does for Eureka
A clear verdict
Not just a number — a plain-English call for Eureka: open the windows, or keep them shut.
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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.
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Most days, the fog belt does the work
Eureka's air quality is usually rated Good, and the reason is geography. The town sits on Humboldt Bay in the coastal fog belt, where cool air pulled in off the Pacific brings frequent thick fog and steady northwesterly winds through the summer. That marine ventilation flushes pollutants out to sea before they can build up, which is why the North Coast air district reports its region is in attainment for the federal ozone, PM2.5 and PM10 standards.
The same ocean air that keeps the redwoods damp keeps Eureka's baseline air clean. On an ordinary day there is little heavy industry, little traffic congestion by California standards, and a constant sea breeze doing the housekeeping. The days that don't feel clean are the exceptions, and they tend to come from two very specific directions: inland fire smoke and winter wood burning.
When the interior burns, the smoke finds the coast
Being on the coast is not the same as being out of reach. In September 2020 the greater Eureka area, from Rio Dell up to Trinidad, was forecast to hit Very Unhealthy air as smoke poured in from a wall of inland fires: the Red Salmon Complex, the record-setting August Complex, the Slater Fire, the Elkhorn/Hopkins Fire and the Oak Fire. When the wind turns and pushes that smoke toward the coast, the marine layer that normally protects the town can instead trap it against the hills.
The August Complex that year was a reminder of how much fuel sits just inland. It began on August 17, 2020 as dozens of lightning strikes on the Mendocino National Forest, grew across the Six Rivers and Shasta-Trinity forests and into Trinity County next door, and eventually burned more than a million acres, the largest wildfire in California's recorded history and the state's first so-called gigafire. Eureka never burned, but for stretches of that September its residents were breathing that fire's smoke.
Winter is wood-smoke season here
The pollutant the local air district worries about most is not wildfire smoke or traffic. It is wood smoke in winter. The North Coast Unified Air Quality Management District, headquartered on L Street in Eureka, describes particulate matter from residential wood burning as the principal pollutant of the North Coast, and the numbers back it up: three of the region's PM-10 exceedances between 2014 and 2019 were traced to woodstove burning.
The problem is a mix of habit and weather. Wood heat is common across Humboldt, and on cold, calm winter nights the same moderate temperatures, fog and rain that make the coast pleasant also create temperature inversions that cap the air and hold smoke close to the ground. On those nights a single neighborhood of chimneys can push local readings well above what the coastline sees the rest of the year, which is exactly the kind of change worth catching before you open the windows.
Eureka air quality FAQ
What is the air quality in Eureka right now?
As of September 5, 2026 at 5:10 AM PDT, the air quality in Eureka, California is AQI 15 — Good — with PM2.5 at 2.7 µg/m³, the median of 5 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Does wildfire smoke reach Eureka even though it's on the coast?
Yes. Eureka's air is usually kept clean by the ocean breeze, but when inland fires burn and the wind turns onshore, smoke can settle over the coast. In September 2020, smoke from the August Complex and several other fires pushed the greater Eureka area, from Rio Dell to Trinidad, into Very Unhealthy air for days at a time.
Why is Eureka's air worse on some winter nights?
The main local pollutant in winter is wood smoke. Wood heat is common across Humboldt, and on cold, calm nights the fog and moderate temperatures create inversions that trap smoke close to the ground. The North Coast air district considers particulate matter from residential wood burning the region's principal pollutant, which is why a still winter evening can read far higher than a typical foggy summer day.
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 Eureka, 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 Eureka
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