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Air & health

Air Quality & AQI by City

Is it safe to be outside today? Each city page leads with the answer — the live AQI, the main pollutant driving it, and a go/no-go for outdoor exercise — then explains how to read the EPA scale so the number actually means something. Built on open Open-Meteo / Copernicus CAMS data — no ads, no app, for 916 cities with an air-quality page.

Air quality by city

The 60 largest by population, of 916 cities with an air-quality page — browse by state below for the rest.

Browse by state

Each state hub lists its cities with an air-quality page, largest first, with each county’s typical AQI from EPA records.

Air quality guides

Plain-language reference on the EPA AQI scale — the six categories and colors, the pollutants behind the number, and how the index is computed from raw concentrations.

Frequently asked

What AQI level is considered safe?
On the EPA's Air Quality Index, 0–50 (Good, green) is safe for everyone and 51–100 (Moderate, yellow) is acceptable for almost everyone, though unusually sensitive people may notice symptoms. 101–150 (orange) is Unhealthy for Sensitive Groups, 151–200 (red) is Unhealthy for everyone, 201–300 (purple) is Very Unhealthy, and 301+ (maroon) is Hazardous. As a rule of thumb, an AQI under 100 is a safe day for outdoor activity.
Should I wear a mask at this AQI?
A mask helps most when fine-particle pollution (PM2.5) is high — for example during wildfire smoke. A well-fitted N95 or KN95 filters the fine particles that cause the most harm; cloth and surgical masks do little against them. Most people don't need a mask below an AQI of 150, but at 151+ (Unhealthy) an N95 is worth wearing outdoors, and at 201+ (Very Unhealthy or worse) it's best to stay indoors with air filtration rather than rely on a mask. Note that masks do not filter ground-level ozone.
Is it safe to exercise outside at this AQI?
Below 100 (Good or Moderate) it's generally fine to run or work out outdoors. From 101–150 (Unhealthy for Sensitive Groups), people with asthma, heart conditions, kids, and older adults should shorten or move workouts indoors. At 151+ (Unhealthy) everyone should cut back on hard outdoor exertion, because exercise makes you breathe more polluted air deeper into your lungs.
What do a Fire Weather Watch and a Red Flag Warning mean for air quality?
Both come from the National Weather Service. A Fire Weather Watch means critical fire-weather conditions — dry fuels, low humidity, gusty wind — are possible in the next day or two; a Red Flag Warning means they're happening or imminent. Wildfire smoke shows up in air-quality data as fine-particle (PM2.5) pollution. On smoky days, EPA and AirNow guidance is to limit time outdoors, keep windows closed, run filtration if you have it, and wear an N95 if you must be outside.