Sources and coverage
Air Quality Watch republishes official public data. Each source keeps its own attribution and terms, and every figure on the site names its source and time.
| Source | What it is | Cadence | Where it appears | Attribution and terms | Vintage |
|---|---|---|---|---|---|
| AirNow current AQI contours | AirNow current AQI contours (PM2.5 and ozone combined), plus the PM2.5 and ozone products: shaded areas interpolated between monitors. | Published hourly; checked every hour | National, state and city maps | Preliminary data; credit U.S. EPA AirNow and partner agencies; values and official colors unaltered. | Current hour |
| AirNow monitor observations | AirNow hourly monitor observations (HourlyAQObs): hourly NowCast AQI and concentrations by monitoring site. | Hourly; checked every hour | Map markers; nearby monitors on city pages | Preliminary data; credit U.S. EPA AirNow and the reporting agency. | Current hour |
| AirNow reporting areas and forecasts | AirNow reporting-area observations and agency forecasts (reportingarea.dat): each reporting area's current AQI and the agency forecasts, with discussions and action days. | Rewritten several times an hour; checked every 15 minutes | Home, state and city pages; forecast map | Preliminary observations; forecasts, discussions and action-day names shown as issued. | Current |
| AirNow reporting area list and ZIP codes | The 945 U.S. reporting areas with locations, forecasting agencies and time zones, and AirNow's ZIP code to reporting area list. | Updated by AirNow daily; rebuilt with the site | Place and ZIP search; page list | Credit U.S. EPA AirNow. | File dated November 12, 2026; downloaded November 12, 2026 |
| National Weather Service alerts | National Weather Service active air quality alerts: Air Quality Alerts, Dense Smoke Advisories and related messages, with their areas and expiry times. | Checked every 5 minutes | Alert sections on home, state and city pages; map overlay | U.S. government work; text shown verbatim with a link to the official alert. | Current |
| EPA AirData annual AQI by county | Yearly counts of days by AQI category for each county with a monitor, 2016–2025. | EPA refreshes about twice a year | History page, history map, state and city history | U.S. government work; credit U.S. EPA AirData. | Data as of June 25, 2026 |
| Census boundaries (us-atlas) | State and county outlines from U.S. Census Bureau cartographic boundary files (2017), packaged as TopoJSON by us-atlas. Connecticut appears with its eight historical counties, matching EPA AirData. | Fixed | Maps; county assignment for city pages | Census data are public domain; us-atlas is ISC licensed. | 2017 boundaries (us-atlas 3.0.1) |
| Census Gazetteer | Place names, New England towns and ZIP Code Tabulation Area centers for search. | Yearly | Place and ZIP search | Public domain. | 2026 Gazetteer; File dated September 8, 2026; downloaded November 12, 2026 |
| NIFC wildland fire incidents | NIFC WFIGS current wildland fire incident locations and interagency perimeters: active wildfires and prescribed fires with reported size, containment and times, and mapped perimeters where published. | WFIGS refreshes from IRWIN every few minutes; checked every 30 minutes | Wildfire sections on state and city pages; map | Credit: Wildland fire incidents and perimeters from the National Interagency Fire Center (WFIGS, IRWIN). U.S. government data, published by NIFC with a disclaimer that the records can change. | Current incidents |
| OpenFreeMap and OpenStreetMap | The street basemap under the interactive map: roads, places and water, from OpenStreetMap data served by OpenFreeMap. | Loaded by your browser when the map is shown | Interactive maps | © OpenStreetMap contributors (ODbL); OpenFreeMap attribution shown on the map. | Current OpenFreeMap build |
State and local agency feeds
Notices from state, county and district air agencies, shown in each agency's own words with its credit line and caveat. Feeds are collected for 13 states: Arizona, California, Colorado, Connecticut, Florida, Idaho, Illinois, Kentucky, Montana, Oregon, Texas, Utah and Washington. Feeds still waiting for the publisher's permission are left out of this list until they are switched on.
| Source | What it is | Cadence | Where it appears | Credit | Caveat |
|---|---|---|---|---|---|
| Maricopa County Air Quality Department, Alert Center and News Flash (Air Quality) | Action days, Arizona | Checked every 30 minutes | State and local notices on the Arizona page and its city pages; map | Maricopa County, Arizona | Alerts are shown for 36 hours after the county posts them; check the county's page for the days a No Burn Day covers. |
| San Joaquin Valley Air Pollution Control District, Check Before You Burn | Burn restrictions, California | Checked every hour | State and local notices on the California page and its city pages; map | San Joaquin Valley Air Pollution Control District | Burn status is a district rule for residential wood burning, set from forecast conditions; registered clean devices may be exempt in some tiers. The burn season runs November through February. |
| Colorado Department of Public Health and Environment, Denver Metro air pollution forecast and advisories | Action days, Colorado | Checked every hour | State and local notices on the Colorado page and its city pages; map | Colorado Department of Public Health and Environment, Air Pollution Control Division | Action Days are forecasts; indoor-burning restrictions cover the seven-county Denver-Boulder area (parts of Adams and Arapahoe) and run "until at least" the time given, so check the page for extensions. |
| Colorado Smoke Outlook blog (CDPHE Air Pollution Control Division) | Smoke outlooks, Colorado | Checked every 30 minutes | State and local notices on the Colorado page and its city pages; map | Colorado Department of Public Health and Environment, Air Pollution Control Division | Agency narrative excerpt; read the full post for advisories and timing. |
| Connecticut DEEP, Forecasted Ozone Exceedance Days | Action days, Connecticut | Checked every hour | State and local notices on the Connecticut page and its city pages; map | Connecticut Department of Energy and Environmental Protection | These are forecasts, not measured exceedances; the restrictions apply to the regulated community, not the public. The ozone season runs March to September. |
| Florida Forest Service, active burn authorizations | Authorized burns, Florida | Checked every hour | State and local notices on the Florida page and its city pages; map | Florida Department of Agriculture and Consumer Services, Florida Forest Service | An authorization gives permission to burn on the stated day; a listed burn may or may not have been lit. Locations are rounded to about 1 km. |
| Idaho Smoke Information blog (interagency) | Smoke outlooks, Idaho | Checked every 30 minutes | State and local notices on the Idaho page and its city pages; map | Idaho Smoke Information blog partners (Idaho DEQ and others) | Agency narrative excerpt; the blog posts mainly in wildfire and prescribed-burn seasons. |
| Open Air Chicago hourly sensor data (City of Chicago Data Portal) | State sensors, Illinois | Checked every 6 hours | State and local notices on the Illinois page and its city pages; map | City of Chicago Department of Public Health and UIC School of Public Health, Open Air Chicago | Neighborhood sensors run by the City of Chicago. These are lower-cost, non-regulatory sensors; readings arrive as a daily batch, use the vendor's calibration only, are not corrected by this site, and can differ from official AQI. |
| Louisville Metro Air Pollution Control District, open burn permits (Louisville Open Data) | Authorized burns, Kentucky | Checked every 2 hours | State and local notices on the Kentucky page and its city pages; map | Louisville Metro Government, Air Pollution Control District (Louisville Open Data) | A permit allows burning on the listed date; it does not mean a fire took place. Locations are rounded to about 1 km. |
| Louisville Metro APCD enforcement data (Louisville Metro Open Data) | Enforcement notices, Kentucky | Checked every 6 hours | State and local notices on the Kentucky page and its city pages; map | Louisville Metro Air Pollution Control District, Louisville Metro Open Data (PDDL) | A notice of violation is an allegation by APCD that can still change; the status and the official record give the outcome. |
| Montana DEQ Today's Air (non-regulatory sensors) | State sensors, Montana | Checked every hour | State and local notices on the Montana page and its city pages; map | Montana Department of Environmental Quality | Non-regulatory sensor readings as Montana DEQ publishes them: preliminary, not quality assured, and aberrant values may be removed later. |
| Oregon Smoke Information blog (interagency) | Smoke outlooks, Oregon | Checked every 30 minutes | State and local notices on the Oregon page and its city pages; map | Oregon Smoke Information blog partners (Oregon DEQ, Oregon Health Authority, ODF, federal and tribal agencies) | Agency narrative excerpt; read the full post for advisory areas and timing. |
| TCEQ Air Emission Event Report Database (RSS feed) | Reported emission events, Texas | Checked every hour | State and local notices on the Texas page and its city pages; map | Texas Commission on Environmental Quality | Each report is the facility's own report to TCEQ and may be amended; it is not a measurement of exposure where people live. |
| TCEQ Air Quality Forecast (forecast discussion) | Forecast discussions, Texas | Checked every 3 hours | State and local notices on the Texas page and its city pages; map | Texas Commission on Environmental Quality | TCEQ's regional forecast narrative, quoted as published; conditions at a given place can differ. |
| TCEQ Emergency Response spills, air incidents (data.texas.gov) | Reported air releases, Texas | Checked every 6 hours | State and local notices on the Texas page and its city pages; map | Texas Commission on Environmental Quality, via data.texas.gov | Reported releases as TCEQ recorded them, with dates only and locations rounded to about 1 km; amounts are reported estimates and may be revised. |
| Utah Division of Air Quality, air quality forecast and action days | Burn restrictions, Utah | Checked every hour | State and local notices on the Utah page and its city pages; map | Utah Department of Environmental Quality, Division of Air Quality | Action days are forecasts set by the Utah Division of Air Quality; county and city rules (such as Salt Lake County Health Regulation 35) may add restrictions. |
| Northwest Clean Air Agency and Olympic Region Clean Air Agency news feeds (burn bans) | Burn restrictions, Washington | Checked every 30 minutes | State and local notices on the Washington page and its city pages; map | Northwest Clean Air Agency; Olympic Region Clean Air Agency | Agency announcements from the last 14 days; a later post may cancel a ban. Other Washington agencies and Ecology announce bans on their own pages. |
| Washington Smoke Blog (state, county, federal and tribal partners) | Smoke outlooks, Washington | Checked every 30 minutes | State and local notices on the Washington page and its city pages; map | Washington Smoke Blog partners (Washington Department of Ecology and others) | Agency narrative excerpt; the blog posts mainly in wildfire season (about June to September). |
Connecticut, Massachusetts and Rhode Island datasets
Facility lists, enforcement records, permits and air-toxics results for the pilot states, copied when the site is built and dated below.
| Dataset | Publisher | Vintage | Where it appears | Credit and terms | Caveat |
|---|---|---|---|---|---|
| Environmental Justice Affecting Facilities 2026 | Connecticut Department of Energy and Environmental Protection (DEEP) | Data as of May 21, 2026; downloaded November 12, 2026 | Connecticut page and its city pages | Credit: Connecticut Department of Energy and Environmental Protection. Public domain dedication (CC0 1.0), as stated on the DEEP item. | A list of permitted or regulated facilities; it measures neither emissions nor exposure. |
| Formal Enforcement Case Summaries 2021-Present | Connecticut Department of Energy and Environmental Protection (DEEP), via data.ct.gov | Data as of July 21, 2026; downloaded November 12, 2026 | Connecticut page; city pages in the town | Credit: CT DEEP via data.ct.gov. Public Domain U.S. Government (license shown on data.ct.gov). | Formal orders, most of them consent orders, which are often settled without an admission of liability. |
| Air Pollution Background 2025 (DEEP monitoring stations) | Connecticut Department of Energy and Environmental Protection (DEEP) | Data as of June 2, 2026; downloaded November 12, 2026 | Connecticut reference data | Credit: Connecticut Department of Energy and Environmental Protection. No license is stated on the item; station identities are factual reference data. | Station names and locations, for reference. |
| ECHO Air Facility Search: Connecticut, active facilities | U.S. Environmental Protection Agency, Enforcement and Compliance History Online (ECHO) | downloaded November 12, 2026 | Connecticut page and its city pages | Credit: U.S. EPA ECHO. U.S. federal government data (EPA); public domain in the United States. | A list of permitted or regulated facilities; it measures neither emissions nor exposure. |
| ECHO Air Facility Search: Massachusetts, active facilities | U.S. Environmental Protection Agency, Enforcement and Compliance History Online (ECHO) | downloaded November 12, 2026 | Massachusetts page and its city pages | Credit: U.S. EPA ECHO. U.S. federal government data (EPA); public domain in the United States. | A list of permitted or regulated facilities; it measures neither emissions nor exposure. |
| ECHO Air Facility Search: Rhode Island, active facilities | U.S. Environmental Protection Agency, Enforcement and Compliance History Online (ECHO) | downloaded November 12, 2026 | Rhode Island page and its city pages | Credit: U.S. EPA ECHO. U.S. federal government data (EPA); public domain in the United States. | A list of permitted or regulated facilities; it measures neither emissions nor exposure. |
| VOC Monthly Averages 2020-2026 | Massachusetts Department of Environmental Protection (MassDEP) | Data as of October 21, 2026; downloaded November 12, 2026 | Massachusetts page; Boston, Essex and Norfolk pages | Credit: Massachusetts Department of Environmental Protection. Mass.gov Terms of Use apply; no specific license is stated on the workbook. Shown as derived monthly summaries with attribution and a link to the source. | Monthly averages at one monitoring site, posted after laboratory analysis; they describe past months at that location. |
| 2020 Environmental Justice Populations (block groups) | MassGIS, for the Executive Office of Energy and Environmental Affairs | Data as of June 2024; downloaded November 12, 2026 | Massachusetts page and its city pages | Credit: MassGIS (Bureau of Geographic Information), Commonwealth of Massachusetts EOTSS. MassGIS data "may be used by anyone for their purposes"; credit required as stated by MassGIS. Not a legal description; no liability is accepted by the Commonwealth. | The designation describes the residents of an area, and says nothing about pollution levels there. |
| MassDEP Major Facilities (BWPMAJOR_PT) | MassGIS, from Massachusetts Department of Environmental Protection data | Data as of March 2024; downloaded November 12, 2026 | Massachusetts page and its city pages | Credit: MassGIS (Bureau of Geographic Information), Commonwealth of Massachusetts EOTSS. MassGIS data "may be used by anyone for their purposes"; credit required as stated by MassGIS. Not a legal description; no liability is accepted by the Commonwealth. | A list of permitted or regulated facilities; it measures neither emissions nor exposure. |
| Major Source Permit Listing (PDF) | Rhode Island Department of Environmental Management (RIDEM), Office of Air Resources | Data as of April 28, 2022; downloaded November 12, 2026 | Rhode Island page | Credit: RIDEM Office of Air Resources. RI.gov public-information wording; linked, not rehosted. | Permits set allowed emissions and operating conditions; they report no actual emissions. |
| Environmental Justice Area 2022 (environmental justice focus areas, census tracts) | Rhode Island Department of Environmental Management (RIDEM), via RIGIS | Data as of 2022; downloaded November 12, 2026 | Rhode Island page and its city pages | Credit: RIDEM / RIGIS. No license is stated on the layer; state regulatory boundaries used with attribution. | The designation describes the residents of an area, and says nothing about pollution levels there. |
| RI Power Plants (RIDEM Regulated Facilities) | Rhode Island Department of Environmental Management (RIDEM), via RIGIS | downloaded November 12, 2026 | Rhode Island page and its city pages | Credit: RIDEM / RIGIS. License "OPEN" on the RIDEM Regulated Facilities service item; credit RIDEM. | Permits set allowed emissions and operating conditions; they report no actual emissions. |
About AirNow data
Current observations come from federal, state, local and tribal air agencies through the U.S. EPA AirNow program. They are preliminary: agencies review them later, and the official record is kept in EPA's Air Quality System. AirNow asks that its data be credited to the agencies and to AirNow, labelled preliminary, shown with the official AQI colors and left unaltered; this site follows those data exchange guidelines. The participating agencies are listed on AirNow's partner page.
Coverage
- AirNow lists 945 reporting areas in the 50 states, Washington, DC and Puerto Rico. Some have current readings, some forecasts, and many both.
- The contour maps cover the lower 48 states and nearby areas; Alaska, Hawaii and Puerto Rico appear with monitors and reporting areas.
- Monitors are dense in cities and sparse in rural areas, so readings far from a monitor rely on interpolation.
- This site has pages for every state, Washington, DC and Puerto Rico, and for 51 cities and reporting areas, starting with Connecticut, Massachusetts and Rhode Island and major metros.
- History covers counties with a monitor; others are shown as no data.
State and local agency notices are carried for 13 states, listed above. Wildfire incidents cover the whole country. Satellite smoke plumes and fire detections are not included.
Wildfire caveat: Fire locations and sizes are as reported by fire managers and can lag events. A perimeter shows the last mapped extent at the stated time; the fire may have moved since, and many fires have no perimeter. A fire on the map does not mean smoke is reaching the ground nearby: check the air quality readings.
Data files
The search and history files the site's own pages use are public JSON: history index, places. Third-party terms above still apply to their contents.