Air Quality in Portland, Maine — Live

Live readings from PurpleAir sensors across Portland and Casco Bay — with free alerts when the air actually changes.

Live Portland AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Portland and South Portland, Westbrook, Falmouth, Scarborough.

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.

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 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, Maine right now?

This page shows the current AQI for Portland, calculated from PurpleAir sensors around the peninsula and surrounding towns and updated continuously. The map below shows every live sensor, so you can check the reading closest to your own neighborhood, whether that's the West End, the East End waterfront, or across the bridge in South Portland.

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 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.

Where does Canairy's Portland data come from?

Readings come from PurpleAir's network of laser particle sensors across Portland and surrounding towns, cross-referenced with government monitors and the Google Air Quality API. You can see every sensor behind your numbers on the live map - there's no black box.

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.