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.

Live Dover AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Dover and Durham, Somersworth, Rochester, Portsmouth.

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.

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.

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?

This page shows the current AQI for Dover, calculated from PurpleAir sensors across the city and updated continuously. The map below shows every live sensor, so you can check the reading closest to your own neighborhood.

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 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 Dover data come from?

Readings come from PurpleAir's network of laser particle sensors across Dover and surrounding Seacoast 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.