Air Quality in Nashua, New Hampshire — Live

Live readings from PurpleAir sensors across Nashua — with free alerts when summer ozone climbs or wildfire smoke rolls in.

Live Nashua AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Nashua and Hudson, Merrimack, Hollis, Amherst.

Most of the year, Nashua's air is genuinely good — flat Merrimack Valley terrain and New England's brisk prevailing winds keep pollution moving through rather than settling in. The exception is summer: on hot, hazy, calm days between April and September, ground-level ozone can build up over southern New Hampshire, some of it made locally by Everett Turnpike traffic baking in the sun, much of it riding in on the same stagnant air mass that has already cooked for a day or two over New York City and Boston. Every few years, smoke drifting down from Quebec adds a second, very different kind of bad-air day that has nothing to do with local weather at all.

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.

Nashua's ozone problem starts hundreds of miles away

New Hampshire is one of thirteen jurisdictions in the Ozone Transport Commission, a multi-state body created under the Clean Air Act in 1991 specifically because ground-level ozone does not respect state lines. Nitrogen oxides and volatile organic compounds from the Washington-to-Boston corridor drift northeast and cook into ozone in the same sunlight that falls on Hillsborough County, so a still, hot day in Nashua can carry a load of smog that started as tailpipe and smokestack exhaust two states away.

The state's own forecasters track this closely: New Hampshire DES issues ozone forecasts every day from April through September, broken out by ten county-level zones, and Hillsborough County — Nashua's zone — gets its own daily call. An Air Quality Action Day is called when that transported ozone combines with local traffic on the Everett Turnpike and Route 3 and the day's heat and sun are enough to push levels into unhealthy territory, typically on the stagnant, high-pressure afternoons of July and August.

The summer of 2023 showed how far wildfire smoke can travel

On June 6, 2023, the EPA issued an air quality alert naming the central, southern, and western parts of New Hampshire — Nashua's part of the state — as likely to exceed the federal 24-hour standard for fine particle pollution, as smoke from record Quebec wildfires poured south into the Northeast on a counterclockwise flow around a low-pressure system. Health officials told sensitive groups to stay indoors with windows closed and avoid strenuous outdoor activity while the haze hung over the region.

New Hampshire's own environmental agency later noted that the state was largely spared the worst of that smoke — the choking, orange-sky days that hit New York and Pennsylvania harder — but it still logged seven separate Air Quality Action Days that summer, well above a typical year. That is the lesson Nashua residents took from 2023: you do not need to be under the thickest part of a Canadian wildfire plume to end up with air that is genuinely unhealthy to breathe.

Winter adds a slower-building particle problem

Ozone and imported smoke are warm-weather stories; winter in Nashua brings a quieter one. Many New Hampshire homes supplement or replace furnace heat with wood stoves and fireplaces, and on cold, calm nights that smoke has nowhere to go. Research on residential wood burning nationally puts it at roughly a fifth of all winter fine-particle pollution, and New Hampshire's own environmental agency has run public advisories urging residents to burn only seasoned wood and keep fires hot enough to burn cleanly, precisely because wood smoke is a measurably bigger piece of the winter air-quality picture than most people assume.

New Hampshire DES has backed that message with action elsewhere in the state — the City of Keene's woodstove changeout program, running since 2009, offered rebates to replace older, dirtier stoves — evidence that state regulators treat wood smoke as a real and addressable source, not just a cozy inconvenience. For a Nashua household that heats with wood, checking the day's PM2.5 reading before a bitter, windless night is as useful a habit as checking it before a smoky August afternoon.

Nashua air quality FAQ

What is the air quality in Nashua right now?

This page shows the current AQI for Nashua, 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 Nashua's air get worse in summer?

Southern New Hampshire sits downwind of the Boston-to-New York corridor, and on hot, calm days from April through September, ozone that forms over that corridor drifts northeast and combines with local traffic on the Everett Turnpike and Route 3. New Hampshire's environmental agency forecasts ozone by county and calls an Air Quality Action Day when the combination of transported and local pollution is expected to reach unhealthy levels.

Did the 2023 Canadian wildfires affect Nashua?

Yes, though less severely than states farther south. On June 6, 2023, the EPA issued an air quality alert for central, southern, and western New Hampshire — which includes Hillsborough County — as smoke from record Quebec wildfires pushed fine particle pollution to unhealthy-for-sensitive-groups levels. New Hampshire logged seven Air Quality Action Days that summer, more than a typical year, even though the state avoided the worst of the smoke that hit New York.

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 Nashua data come from?

Readings come from PurpleAir's network of laser particle sensors across Nashua 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.