Air Quality in Missoula, Montana — Live

Live readings from PurpleAir sensors across Missoula — with free alerts when winter inversions or wildfire smoke roll into the valley.

Live Missoula AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Missoula and Lolo, Frenchtown, Bonner, East Missoula.

Missoula sits at the hub of five valleys, where the Bitterroot, Sapphire, Garnet, and Rattlesnake ranges converge around three rivers, and most of the year the air here is genuinely clean. The trouble shows up at both ends of the calendar: cold, still nights from November through February trap wood smoke against the valley floor, and dry summers can bring wildfire smoke down from the surrounding forests. The same mountain ring that makes Missoula beautiful is what holds bad air in place once the wind stops.

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 Missoula's winters trap wood smoke

Missoula sits in a bowl at the convergence of the Bitterroot, Sapphire, Garnet, and Rattlesnake ranges - locals call it the hub of five valleys. On cold, calm nights that ring of mountains holds a temperature inversion in place over the valley floor, and instead of rising and dispersing, smoke from chimneys sinks and pools right where people are breathing it. The city and county recognized the problem early: Missoula's Air Stagnation Zone was designated in 1981, and it still extends roughly four miles beyond the city limits today.

In 1994, the county banned installing new wood stoves inside that zone altogether - only EPA-certified pellet stoves and gas appliances are allowed for new installations, and an existing non-compliant stove has to be removed when a property is sold. A 2006-2007 study of Missoula's winter air found residential wood burning responsible for 55 percent of wintertime PM2.5, with ammonium nitrate (18 percent) and industry (19 percent) making up most of the rest. The county also requires oxygenated fuel blends for vehicles every November through February - the valley's winter pollution problem was never just one source.

Stage I and Stage II air alerts

When wood smoke starts to build up inside the Air Stagnation Zone, Missoula City-County Health steps in with a two-tier alert system. A Stage I alert bars any visible smoke from a fireplace, wood stove, or other solid-fuel device within the zone unless the owner holds a specific permit. If conditions worsen, a Stage II alert extends the restrictions across the larger Impact Zone M, a wider ring around the valley.

These aren't hypothetical rules - they get called on real winter days when the inversion locks in and the valley's monitors start climbing. If you heat with wood, or you're just trying to decide whether to keep the windows shut, knowing which stage is in effect matters more here than in most towns, because the same still air that traps smoke also means one side of the valley can be noticeably worse than another at the same hour.

Wildfire smoke has its own bad years

Missoula's other air problem comes from farther away. The county's own health department points to 2000, 2003, 2007, 2012, and 2015 as its worst wildfire-smoke years, when fires burning across western Montana and the wider Northern Rockies filled the valley with smoke for days at a stretch. In a severe fire season, that summer smoke - not winter wood burning - becomes Missoula County's single biggest source of PM2.5 pollution for the year.

Unlike the wood-smoke season, wildfire smoke doesn't need a local inversion to make itself felt - a large fire burning in Idaho or western Montana can fill the valley with haze even when the sky over Missoula itself is empty of flame. Because it's driven by whatever happens to be burning that particular summer, the timing and severity vary a lot from one year to the next, which is exactly why Canairy tracks the sensors continuously instead of asking you to remember which years were bad.

Missoula air quality FAQ

What is the air quality in Missoula right now?

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

Why does Missoula get smoky in winter?

Missoula sits in a bowl surrounded by the Bitterroot, Sapphire, Garnet, and Rattlesnake ranges, and on cold, calm nights that geography traps a temperature inversion over the valley floor. Smoke from wood stoves and fireplaces has nowhere to go, which is why the county designated an Air Stagnation Zone in 1981 and banned new wood stove installations inside it in 1994.

Which wildfires have hit Missoula's air quality hardest?

Missoula County's health department points to 2000, 2003, 2007, 2012, and 2015 as the worst wildfire-smoke years, when fires across western Montana and the Northern Rockies filled the valley with smoke for days at a time. In a bad fire season, that summer smoke becomes the county's single largest source of PM2.5 for the year, outweighing even the wintertime wood-smoke problem.

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 Missoula data come from?

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