Air Quality in Gaithersburg, Maryland — Live

Live readings from PurpleAir sensors across Gaithersburg — with free alerts when summer ozone or wildfire smoke moves in.

Live Gaithersburg AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Gaithersburg and Rockville, Germantown, Montgomery Village, North Potomac.

Gaithersburg's air is unremarkable for most of the year — this is a Piedmont suburb of Washington, D.C., with no refineries, ports, or heavy industry, and Montgomery County's gently rolling terrain doesn't trap air the way a mountain valley does. The two things that actually move the needle here are summer heat cooking up ground-level ozone along the region's highway corridors, and the occasional summer stretch when smoke from Canadian wildfires drifts hundreds of miles south and turns a clear sky hazy.

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.

Ozone, not smoke, is the recurring problem here

Gaithersburg sits entirely within Montgomery County's Piedmont, a stretch of gently rolling terrain that doesn't box in air the way a mountain valley does — there's no ring of hills here holding a temperature inversion in place for days. What Gaithersburg does have is a humid subtropical climate with summer afternoons that average around 85°F, and a spot right on the I-270 corridor, which carries more than 250,000 vehicles a day where it crosses the Rockville interchange just south of the city.

That combination — heat, sun, and a steady stream of tailpipe exhaust — is what cooks up ground-level ozone, the pollutant that drives most of the Washington, D.C. region's bad-air days. I-270 has only gotten busier since a 1990s widening project pulled more homes and businesses up the corridor as far as Germantown, and on hot, still, sunny afternoons the ozone that forms over the highway can push the AQI into Moderate or worse territory well before evening rush hour.

Canadian wildfire smoke has reached Gaithersburg more than once

Gaithersburg has no fires of its own, but it doesn't need one. In June 2023, smoke from wildfires burning in Nova Scotia reached Washington, D.C. and its Maryland suburbs by June 2, and by June 8 it had thickened into some of the worst air quality the region had seen in years — thick enough to postpone a Washington Nationals game that night and put the whole Philadelphia-DC-Trenton corridor under some of the country's worst air. Maryland recorded a measurable spike in cardiopulmonary emergency visits during the two worst stretches that summer, June 6-8 and June 28-30.

That wasn't a one-off. The Metropolitan Washington Council of Governments, which runs the region's air-quality alerts, issued another Code Purple day — its second-highest alert level — on July 17, 2026, again citing smoke drifting down from Canadian wildfires for a spike in fine particle pollution. Gaithersburg is hundreds of miles from the nearest Canadian fire, but smoke this fine doesn't need to be local to be dangerous; it rides in on the jet stream and settles over the whole region at once.

What actually helps on a bad-air day here

Ozone in Gaithersburg follows a predictable clock: it builds through the afternoon as sunlight bakes the day's traffic exhaust, and it is usually worst between roughly 2 and 6 p.m. on hot, sunny days with little wind. Shifting an outdoor run or a kid's practice to the morning, before the ozone has had time to form, is a genuinely useful move on a Code Orange day here — a direct response to how this specific pollutant behaves, not just generic advice.

Wildfire smoke doesn't follow that clock — a plume of Canadian smoke can settle over the area in the morning and sit there all day regardless of temperature. That's the real value of checking a sensor before committing to plans instead of judging by how the sky looks: on a hazy summer day here, the difference between ozone that will clear by evening and smoke that's going to sit on the region all day isn't something you can tell just by squinting at the sun.

Gaithersburg air quality FAQ

What is the air quality in Gaithersburg right now?

This page shows the current AQI for Gaithersburg, 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 or your kids' school.

Why does Gaithersburg's air get hazy in summer?

Most of Gaithersburg's bad-air days come from ground-level ozone, not smoke. Hot, humid, sunny afternoons — Montgomery County averages around 85°F on summer days — cook vehicle exhaust from I-270 and the Capital Beltway into ozone, and it tends to peak in the mid-afternoon on still, sunny days rather than overnight.

Does wildfire smoke reach Gaithersburg?

Yes, even though there's no fire anywhere nearby. In June 2023, smoke from wildfires in Nova Scotia gave the Washington, D.C. region, including Gaithersburg, some of its worst air quality in years, and Maryland saw a real spike in emergency visits for heart and lung problems that month. The region's air-quality alert system flagged another Canadian-smoke Code Purple day as recently as July 2026, so it's a recurring risk, not a one-time event.

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 Gaithersburg data come from?

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