0–50 (green) is good for most people. 51–100 (yellow) is moderate. 101–150 (orange) is unhealthy for sensitive groups. 151 and above is unhealthy for everyone, with increasing severity.

Where does this air quality data come from?

EPA AirNow, which aggregates regulatory monitors run by state and local agencies. Alto does not convert or estimate the reading.

Why is my ZIP missing a reading?

AirNow only covers the United States, and some rural ZIPs have no nearby monitor. Try a neighboring city ZIP, or check the map on airnow.gov.

How often does AQI update?

Typically hourly. This page caches a ZIP for about 30 minutes so a refresh does not hammer the API. For a wildfire day, AirNow itself is the faster source.

Weather

Air Quality by ZIP Code

Current Air Quality Index for any U.S. ZIP code, from EPA AirNow.

Enter a U.S. ZIP code and this tool returns the current Air Quality Index from EPA AirNow — the number, the color category, and the health message that goes with it. Rural ZIPs often report from the nearest city monitor.

AQI is a 0–500 scale. Green (0–50) is good for almost everyone. Orange (101–150) is when sensitive groups should cut back outdoor exertion. Purple and maroon are rare and serious.

What the number measures

AirNow reports the highest current pollutant at the nearest monitor, usually fine particles (PM2.5) or ozone. The overall AQI on this page is that highest reading, because that is the one that sets the local color. Individual pollutant values are listed when more than one is reported.

ZIP is not a backyard sensor

A ZIP code can cover many miles, and the reading comes from a regulatory monitor that may sit in the next town. Wildfire smoke and inversions can also change faster than the hourly update. If you are in a sensitive group, treat orange and worse as a reason to check AirNow and your doctor, not as a guess from a neighbor's station.

This is not a medical diagnosis

The health messages are EPA's published categories, not a personal recommendation. People with asthma, heart disease, or young children are the ones the orange and red bands are written for.

Latest Weather & Air Quality News

Air Quality by ZIP — Frequently Asked Questions

What is a good AQI?: 0–50 (green) is good for most people. 51–100 (yellow) is moderate. 101–150 (orange) is unhealthy for sensitive groups. 151 and above is unhealthy for everyone, with increasing severity.
Where does this air quality data come from?: EPA AirNow, which aggregates regulatory monitors run by state and local agencies. Alto does not convert or estimate the reading.
Why is my ZIP missing a reading?: AirNow only covers the United States, and some rural ZIPs have no nearby monitor. Try a neighboring city ZIP, or check the map on airnow.gov.
How often does AQI update?: Typically hourly. This page caches a ZIP for about 30 minutes so a refresh does not hammer the API. For a wildfire day, AirNow itself is the faster source.

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