Air Quality in South Portland, Maine — Live
Live readings from PurpleAir sensors across South Portland — with free alerts when the air quality index changes enough to matter.
AQI 30 from 5 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in South Portland, Maine is AQI 30 — Good and falling — with PM2.5 at 5.4 µg/m³, the median of 5 live PurpleAir sensors reading 16 to 31. 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 South 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 South Portland and Portland, Cape Elizabeth, Scarborough, Westbrook. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in South Portland
The sensors Canairy reads in South Portland agree right now — all 5 sit in the Good band, a 15-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 1.7 mi S | 30 | Good |
| 2.2 mi E | 30 | Good |
| 3.0 mi NNW | 31 | Good |
| 3.2 mi NNW | 25 | Good |
| 4.6 mi N | 16 | Good |
South Portland's air is genuinely good most of the year. The city sits on the western edge of Casco Bay, and the sea breeze off the water tends to clear out whatever haze builds up on a hot afternoon. What makes South Portland's air story different from most New England towns isn't smoke - it's the working waterfront. More than 120 petroleum storage tanks line the shore here, part of the terminal that has fed the Portland-Montreal Pipe Line since 1941, and residents living near them have spent years asking state regulators a simple question: is the air actually safe to breathe.
What Canairy does for South Portland
A clear verdict
Not just a number — a plain-English call for South 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 South Portland or across the country, on one screen.
South Portland's real air story is a tank farm, not a fire season
The waterfront terminal that anchors South Portland's economy stores crude oil in a cluster of tanks along the shore - more than 120 of them citywide - built to feed the 236-mile Portland-Montreal Pipe Line to Quebec refineries. Tank farms like this breathe: as oil moves in and out, volatile compounds including benzene and naphthalene can vent off, and for the neighborhoods closest to the shoreline that has been a documented concern for years, not a hypothetical one.
It came to a head in 2019. At an April 16 South Portland City Council workshop, residents said they were smelling odors from the petroleum storage facilities and wanted air monitoring inside city limits; Portland officials raised the identical complaint about the same facilities that August. Maine's Department of Environmental Protection agreed to help and stood up the South Portland/Portland VOC Monitoring Project, built specifically to measure the volatile organic compounds behind those odors and answer, in the agency's own words, whether the air is safe to breathe.
Why South Portland fought over tar sands instead of wildfire smoke
The same tank farm produced the city's biggest environmental fight of the last decade. After a 2013 ballot measure to block Canadian tar sands crude narrowly failed, the City Council passed a revised Clear Skies Ordinance in July 2014 banning the bulk loading of crude oil onto tankers at the waterfront terminal. The worry wasn't abstract: exporting heavier tar sands crude would have required heating the storage tanks to keep it liquid, meaning more emissions from a facility that already sat close to homes. The pipeline company spent roughly $650,000 fighting the ordinance in court; South Portland won the final round in 2021.
That fight is the opposite of the wildfire story that dominates air-quality pages for a lot of the country. There's no fire season to track here, and no smoke plume that blankets the whole city for a week. The exposure that worries South Portland residents is hyper-local - tied to specific streets near the tank farm, like Ferry Village and Knightville along Mill Creek - rather than a citywide event that reads the same for everyone.
The geography that keeps most days clear
South Portland sits low - about 59 feet at its highest point - on a small, flat peninsula bordered by Portland across the harbor, Cape Elizabeth and Scarborough to the south, and Westbrook inland to the west. There's no mountain ring or valley floor here to trap air the way it does in a lot of Western cities; Casco Bay's open water and onshore breeze do much of the work of clearing the air on their own. The Portland Jetport's main runway actually sits within South Portland's city limits - one more reminder that this is a working peninsula, not a quiet suburb.
Maine's environmental agency notes that ozone runs highest in the warmer months statewide and that fine-particle pollution can rise at any time of year, so summer is still worth watching even without a wildfire season. Because South Portland's real pollution risk is site-specific rather than citywide, a single official monitor miles away won't tell you much about the block you actually live on - which is the reason to check the sensor nearest your own street instead of one citywide number.
South Portland air quality FAQ
What is the air quality in South Portland right now?
As of September 14, 2026 at 8:10 AM EDT, the air quality in South Portland, Maine 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.
Why does part of South Portland smell like petroleum?
South Portland's waterfront is home to more than 120 petroleum storage tanks feeding the Portland-Montreal Pipe Line, and volatile organic compounds like benzene and naphthalene can vent off them. After residents raised the issue at a 2019 City Council workshop, Maine's Department of Environmental Protection launched the South Portland/Portland VOC Monitoring Project to measure those emissions directly rather than rely on a single distant monitor.
What was South Portland's tar sands fight about?
In July 2014, the City Council passed the Clear Skies Ordinance banning the loading of crude oil onto tankers at the waterfront terminal, largely to stop the export of heavier Canadian tar sands crude. Processing that oil would have meant heating storage tanks near residential neighborhoods, raising the risk of more emissions - the pipeline company fought the ordinance in court for years before South Portland won in 2021.
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 South 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 South Portland
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