About OpenAir

Current Air Quality Index (AQI), today and tomorrow forecasts, and hourly monitor readings for about 870 U.S. reporting areas, from preliminary EPA AirNow data.

Where the data comes from

OpenAir uses the public data files of the U.S. Environmental Protection Agency's AirNow program: the reporting area file (current AQI, yesterday's highest AQI and daily forecasts for each reporting area) and the hourly observation files (NowCast AQI and concentrations at each monitor). AirNow gathers these data from more than 150 federal, state, local and tribal air quality agencies, which own the data and issue the forecasts. The full list is at AirNow partners.

Data: U.S. Environmental Protection Agency (EPA) AirNow program and the federal, state, local and tribal air quality agencies that report to it (see airnow.gov/partners). AirNow data are preliminary, not fully verified, and subject to change; they are not official regulatory data. These agencies do not endorse OpenAir.

How often it updates

We download the AirNow files about once an hour and rebuild the site when anything changes. Each page shows the time of the reading it uses. Area pages can also load the newest AirNow file directly in your browser.

What we change, and what we don't

AQI values, categories, forecasts and Action Day flags are shown as received. We add our own plain-language summaries of EPA's AQI categories, the highest reading among nearby monitors for each hour, and links to related pages. We do not use AirNow or EPA logos or maps, and we do not republish forecast discussions; read those on AirNow.gov.

Who runs this site

OpenAir is part of OPENBLOG, a family of free information sites. The site is supported by advertising. Questions or corrections: [email protected].