Air Quality in Portland, Maine — Live
Live readings from PurpleAir sensors across Portland and Casco Bay — with free alerts when the air actually changes.
AQI 18 from 3 PurpleAir sensors · Trending up · data from PurpleAir
As of , the air quality in Portland, Maine is AQI 18 — Good and rising — with PM2.5 at 3.2 µg/m³, the median of 3 live PurpleAir sensors reading 14 to 18. 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 Portland: 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 Portland and South Portland, Westbrook, Falmouth, Scarborough. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Portland
The sensors Canairy reads in Portland agree right now — all 3 sit in the Good band, a 4-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 3.0 mi WSW | 18 | Good |
| 4.9 mi WNW | 18 | Good |
| 5.7 mi NW | 14 | Good |
Portland's air is good most of the year. The city sits on a peninsula in Casco Bay, and the sea breeze off the Gulf of Maine tends to flush out whatever builds up over the harbor and the peninsula. But two things can change that: hot, still summer days when ozone drifts in from hundreds of miles to the south and west, and — as Maine found out twice in 2023 — smoke from Canadian wildfires that can settle over the whole state for days at a time.
What Canairy does for Portland
A clear verdict
Not just a number — a plain-English call for Portland: 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 Portland or across the country, on one screen.
Why does Maine call itself the "tailpipe of the nation"?
Maine sits at the far end of a long air pollution transport corridor. On hot, sunny days, emissions from power plants, industry, and traffic well to the south and west get carried northeast on the prevailing wind. Maine's own Department of Environmental Protection has said pollution transported into the state is a "significant contributor to elevated ozone levels along Maine's coast" — and in 2018, then-Attorney General Janet Mills sued the EPA over delays in designating areas affected by that transported ozone. Maine has also formally petitioned to remove parts of the state from the federal Ozone Transport Region.
The nickname makes it sound worse than it usually is. Portland and the rest of southern Maine actually rank well against most of the country for air quality on an average day — this is a specific summer weather pattern to watch for on hot, hazy, low-wind afternoons, not a year-round condition. It's also why a coastal breeze on a summer day is genuinely good news for your lungs, not just the beach.
What's behind South Portland's tank farms on the waterfront?
Directly across the harbor from downtown Portland, South Portland is, by its own description, the northernmost oil port in the United States, with more than 120 petroleum storage tanks and the Portland–Montreal Pipe Line running through it. Tank farm emissions of benzene and naphthalene have been a documented concern for long enough that Maine DEP runs a dedicated South Portland/Portland VOC Monitoring Project there, separate from its general statewide air network.
This is a narrower, more local story than ozone transport or wildfire smoke — it's a point source, not a weather pattern, so wind direction across the harbor matters a lot. A reading taken on the East End waterfront can look different from one taken a mile inland on the same afternoon, which is exactly the kind of gap a single citywide AQI number papers over and a network of local sensors doesn't.
Has Canadian wildfire smoke reached Portland before?
Yes, and not just once. In June 2023, dense smoke from wildfires burning in Canada pushed poor air quality into the Northeast, and Maine DEP tracked it closely even as the worst of it stayed mostly north and west of the state. Smoke returned that September: on September 6, 2023, DEP issued an alert for a "dense, ground-level plume of smoke from fires in Canada" that pushed northern Maine into Unhealthy for Sensitive Groups territory, and smoke rolled back in again on September 28.
Portland and the rest of southern Maine generally stayed in the Moderate range during both 2023 events rather than the worse levels northern Maine saw — but Moderate is still a real change from Portland's typical Good days, and it's exactly the kind of shift that's easy to miss if you're not looking. It's not an annual certainty here the way it is out west, but 2023 showed it can happen more than once in a single season.
Portland air quality FAQ
What is the air quality in Portland right now?
As of September 14, 2026 at 6:10 PM EDT, the air quality in Portland, Maine is AQI 18 — Good — with PM2.5 at 3.2 µg/m³, the median of 3 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why is Maine sometimes called the "tailpipe of the nation"?
Maine sits at the end of a well-documented air pollution transport corridor - emissions from power plants and traffic to the south and west can blow northeast on hot, still summer days. Maine DEP has said transported pollution is a significant contributor to elevated ozone along the state's coast, and the state has petitioned the EPA and sued over how that ozone gets regulated. Despite the nickname, Portland's air is good on most days of the year - this is a specific summer pattern to watch for, not a constant problem.
Does wildfire smoke from Canada reach Portland?
It can. In June and again in September 2023, smoke from wildfires burning in Canada drifted into Maine, prompting Maine DEP air quality alerts for a dense, ground-level smoke plume. Northern Maine saw the worst of it, reaching Unhealthy for Sensitive Groups, while Portland and the rest of southern Maine mostly stayed in the Moderate range. It isn't an annual certainty the way it is out west, but 2023 showed it can happen more than once in a single season.
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 3 curated PurpleAir sensors Canairy tracks in and around Portland, 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 Portland
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