Weather Story

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, across 31,257 U.S. cities.

Air quality by city

The largest U.S. cities by population. Every city in the corpus has an air-quality page at /air-quality/[state]/[city].

Browse by state

Every state hub lists all of its cities’ air-quality pages, largest first.

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.

Air quality questions, answered

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.