Air Quality in Dover, New Hampshire — Live
Live readings from PurpleAir sensors across Dover — with free alerts when Canadian wildfire smoke or summer ozone moves in.
AQI 31 from 4 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in Dover, New Hampshire is AQI 31 — Good and falling — with PM2.5 at 5.6 µg/m³, the median of 4 live PurpleAir sensors reading 1 to 43. 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 Dover: 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 Dover and Durham, Somersworth, Rochester, Portsmouth. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Dover
The sensors Canairy reads in Dover agree right now — all 4 sit in the Good band, a 42-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 0.7 mi SSE | 31 | Good |
| 5.9 mi WNW | 1 | Good |
| 7.3 mi SE | 31 | Good |
| 8.7 mi SE | 43 | Good |
Most of the year, the air over Dover is unremarkable in the best way — the textile mills that once ran along the Cochecho River closed in 1937, and nothing has replaced them as a major local source of pollution. The two things that actually move the needle here come from somewhere else entirely: ground-level ozone that rides the sea breeze up from the Boston-to-New York corridor on hot summer afternoons, and Canadian wildfire smoke that has twice in three years turned Seacoast skies hazy and prompted state air quality alerts.
What Canairy does for Dover
A clear verdict
Not just a number — a plain-English call for Dover: 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 Dover or across the country, on one screen.
Dover's ozone problem is really Boston's ozone problem
When the EPA tightened the ozone standard in 2015, Strafford County — Dover's county — was grouped with Rockingham, Hillsborough, and Merrimack counties into the Boston-Manchester-Portsmouth (Southeast New Hampshire) nonattainment area. That designation has nothing to do with anything Dover itself puts into the air. Research on the region's summer weather shows sea breezes develop on roughly a third of summer days, and they carry ozone and its precursors north from the Boston metro and the highway corridor beyond it, concentrating along the New Hampshire and Maine coast by afternoon.
That's why a hot, sunny, light-wind day in July is the pattern to watch for in Dover, not smokestacks or traffic. New Hampshire's Department of Environmental Services has issued Code Orange, Unhealthy for Sensitive Groups forecasts for the Seacoast on days when Boston's own air was still only Moderate — the ozone simply arrived a few hours after it formed somewhere else.
Canadian wildfire smoke has found Dover twice in three years
In June 2023, smoke from roughly a dozen wildfires burning in Nova Scotia — several of them uncontrolled — drifted south and gave New Hampshire the orange-tinted skies that made national news across the whole Northeast that summer. The Seacoast was initially spared the worst of it while central and western parts of the state saw the steepest AQI spikes, but the region stayed under watch as the plume shifted with the wind.
It happened again in July 2026: New Hampshire declared Code Orange air quality alerts on July 15 and again on July 17 as fresh smoke from Canadian wildfires settled over the state, with NHPR, WMUR, and local outlets all advising residents to limit time outdoors. Two events in three years doesn't make Dover a wildfire town the way parts of the West are, but it does mean the smoke season most Granite Staters used to associate only with distant fires now shows up as a real, if occasional, entry on the local forecast.
The rivers that shaped the town don't shape its air much anymore
Dover sits low and flat by New England standards — an average elevation of about 49 feet, with the Cochecho and Bellamy rivers draining into the tidal Piscataqua that forms the state line with Maine. There's no valley here to trap smoke or hold a winter inversion the way inland New England mill towns sometimes do; the terrain is coastal plain, open to the sea breeze in summer and to clearing Atlantic weather systems the rest of the year.
That geography, combined with the mills having closed nearly ninety years ago, is a big part of why Dover's baseline air quality reads Good on PurpleAir and government monitors most days of the year. The exceptions are real and worth tracking, but they are exceptions — imported ozone on the hottest, stillest summer afternoons, and smoke on the handful of days a Canadian fire season sends it this far south.
Dover air quality FAQ
What is the air quality in Dover right now?
As of September 14, 2026 at 8:10 AM EDT, the air quality in Dover, New Hampshire is AQI 31 — Good — with PM2.5 at 5.6 µg/m³, the median of 4 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why does Dover's sky get hazy in summer?
Two separate things cause it. On hot, sunny days with a sea breeze, ground-level ozone that formed over the Boston-to-New York corridor rides the coastal wind north and settles over the Seacoast by afternoon. Separately, in some summers - 2023 and again in July 2026 - smoke from wildfires burning in Canada has drifted far enough south to trigger Code Orange air quality alerts across New Hampshire, including Dover.
Does Dover have its own local sources of air pollution?
Not really. Dover's 19th-century textile mills, once a major regional industry, closed in 1937 and have since been converted to housing and offices. Most days the city's air quality is Good, and the notable exceptions - summer ozone and occasional wildfire smoke - both arrive from outside the region rather than from anything local.
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 4 curated PurpleAir sensors Canairy tracks in and around Dover, 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 Dover
We watch Dover's air. You live your life.
Set your threshold once and get a heads-up only when the air actually changes for you. Free on the App Store & Google Play.