EPA AirNow

1. AirNow covers the United States, Canada and Mexico; over 2,500 monitoring stations; forecasts for more than 500 cities; more than 150 local, state, tribal, provincial and federal agencies; data not fully verified or validated, preliminary, not for regulation, trends, guidance or government or public decision making; official data from AQS docs.airnowapi.org
2. Web services list: current forecasts by reporting area, lat/long or ZIP; historical forecasts; PM2.5, ozone and combined KML contour maps; observations by monitoring site (hourly and daily bounding box); current observations by reporting area and by ZIP or lat/long; historical observations by state docs.airnowapi.org
3. API key at top right of Web Services page; users must follow the Data Use Guidelines; per-key per-service hourly rate limits that cannot be changed; observations updated hourly, available 10-30 minutes past the hour; forecasts daily; cache results; reporting areas from part of a city to a county; forecasts not available for every area; area observation is the maximum across its monitors; ZIP and lat/long services return the reporting area peak AQI; do not loop over ZIP codes; reportingarea.dat on files.airnowtech.org updated at :55 and :25; cityzipcodes.csv updated daily docs.airnowapi.org
4. Account required for web services and feeds; activate with emailed confirmation code; key on Web Services page; NowCast AQI per pollutant; CSV, JSON or XML output; six web services retired in September 2026; file products on files.airnowtech.org docs.airnowapi.org
5. New services from June 17, 2026: /aq/forecast/current/, /aq/observation/current/racode/, /aq/observation/current/ziplatlong/, /aq/observation/historical/state/, /aq/dailydata/, /aq/forecast/historical/; six older services (e.g. /aq/observation/latLong/current/) retired September 30, 2026; /aq/data/ and /KML/PM25/, /KML/Ozone/, /KML/Combined/ remain docs.airnowapi.org
6. Data Use (Exchange) Guidelines: preliminary data, not for regulation or decision-making; agencies own the data; credit agencies and EPA AirNow; do not alter values or advisories; use AQI colours; label products preliminary; notify agencies and EPA AirNow of reliance; keep contact details current docs.airnowapi.org
7. Account request form: name, user name, email, phone, agency, comment; must agree to the Data Use Agreement and the EPA AirNow Data Use Guidelines docs.airnowapi.org
8. AQI categories and colours; real-time values are NowCast AQI; forecasts issued by agencies per reporting area; action days docs.airnowapi.org
9. Keyless live check 2026-10-26 (04:59 UTC 27 Oct): 7,410 rows of current observations and forecasts by reporting area, newest observations for 00:00 EDT 27 Oct, last modified 04:42 UTC; US states plus Mexicali (MX) files.airnowtech.org
10. Keyless hourly site file: 4,416 sites with country codes (US 2,726, CA 343, MX 75, others), AQI for ozone/PM10/PM2.5/NO2 and concentrations incl. CO and SO2 files.airnowtech.org
11. ZIP to reporting area lookup file with ZIP centroids, no key files.airnowtech.org
12. A keyless call to the new current-observations service returns HTTP 401 'Request not authenticated.' (tested 2026-10-26) www.airnowapi.org
13. No first-party MCP server; third-party io.github.pipeworx-io/airnow (v0.1.5, remote https://gateway.pipeworx.io/airnow/mcp) registry.modelcontextprotocol.io

About. The U.S. EPA's AirNow program serves real-time Air Quality Index readings (NowCast AQI) and agency-issued AQI forecasts from more than 2,500 monitoring stations run by over 150 local, state, tribal, provincial and federal agencies across the United States, Canada and Mexico. Keyless hourly files (reportingarea.dat by reporting area, HourlyAQObs and HourlyData by monitoring site) download from files.airnowtech.org; the AirNow API web services (by ZIP, lat/long, reporting area or bounding box) need a free account and key. The data are preliminary and unvalidated.

Price. Free. The file products on files.airnowtech.org download without a key; the web services need a free AirNow API account and key.

Coverage. AirNow covers the United States, Canada and Mexico. AQI by reporting area (reportingarea.dat and the ZIP/lat-long services) is for US reporting areas plus Mexicali; Canadian and most Mexican data appear as monitoring sites in the hourly site files. Reporting areas range from part of a city to a whole county, and the lat/long and ZIP services return the reporting area's peak value, not the nearest monitor. Forecasts are not issued for every area, every day or every season.

Timing. AirNow FAQ: "air quality observations for the previous hour are generally available between 10 and 30 minutes past the hour."

Licence. EPA AirNow Data Exchange Guidelines (PDF, Aug 2025) (account sign-up also requires agreeing to a Data Use Agreement): the data are preliminary, not fully verified or validated, and must not be used for regulation, trends, guidance or other government or public decision-making (official data come from EPA's AQS). The federal, state, local and tribal agencies own the data. Users must credit those agencies and EPA AirNow, disseminate values and advisories unaltered, use the AQI colours, label displays and products as preliminary, tell the agencies and EPA AirNow when products rely on the data, and keep their contact details current. AI training and resale are not mentioned.