Airshed · EPA AirNow’s monitors, read live
The air at your ZIP code,
read off the monitors.
Type a ZIP code and this page reads you the air: the Air Quality Index now, its category in the Environmental Protection Agency’s own words and colours, the pollutant that is driving it, and what that category means for the people EPA calls sensitive groups. Under it are the nearest monitors that are actually reporting, each with its distance and the hour it measured, and the forecast for today and tomorrow where a state, local or tribal air agency publishes one.
Every figure is EPA AirNow’s, from the public files AirNow rewrites through the hour, and every figure carries its time. The numbers are preliminary, as AirNow says of all its real-time data. Where no agency reports for a ZIP and no monitor stands near it, the page says exactly that. A computer model’s estimate is shown further down, and is labelled as a model wherever it appears.
27,000 ZIP codes in AirNow’s own list · some 2,000 monitors reporting each hour · observations hourly, forecasts daily · preliminary data, never a guess
The air now
One ZIP code, one reading.
AirNow files every ZIP code it covers under a reporting area — a city, a county or a valley an air agency answers for — and gives each area one Air Quality Index an hour: the highest reading among that area’s monitors, pollutant by pollutant. The largest of those is the number below, and the pollutant it belongs to is the one driving the air.
Air quality by ZIP code
Waiting for a ZIP code
Five digits. Your location is asked for only if you press its button, and is rounded to about a kilometre before it leaves this page.
The reading appears here once you give a ZIP code. If you have, and this line stays, the page’s script did not load — reload the page.
The forecast
Today and tomorrow, where an agency says.
Air quality forecasts are written by state, local and tribal air agencies and passed to AirNow, usually by early afternoon. Not every reporting area has one, some are seasonal, and some give a category without a number. What an agency sent is printed here as it was received, with the day it is for and the day it was issued; where there is none, the page says so and does not fill the gap.
The agency’s forecast
The forecast for a ZIP code appears here once you have asked for one above.
The monitors
The nearest that are reporting.
A reporting area’s number is its worst monitor’s. These are the monitors themselves: the nearest to the centre of the ZIP code that sent AirNow a reading in the last three published hours, with the straight-line distance, each pollutant’s index at that monitor, and the hour it was measured. A monitor that has gone quiet is left out, and when nothing within fifty miles is reporting, that is what this says.
Monitors, nearest first
The monitors near a ZIP code appear here once you have asked for one above.
The model · not a measurement
Three days ahead, modelled.
Monitors say what the air was an hour ago, where they stand. A model fills the map and the days ahead. This panel is the Copernicus Atmosphere Monitoring Service’s forecast, as Open-Meteo serves it, turned into a US index by Open-Meteo: an estimate for a grid square some tens of kilometres across, not a reading from any monitor. It can disagree with the reading above, and when it does the monitors are the measurement.
Modelled index, hour by hour
The model’s estimate for a ZIP code appears here once you have asked for one above.
The scale
Six categories, in EPA’s own words.
The Air Quality Index runs from 0 upward; 100 is, for each pollutant, about the level of the national short-term standard that protects public health. EPA divides the scale into six categories and gives each a colour. The sentences below are EPA’s, from its AQI Basics table, and the colours are the red, green and blue values EPA specifies.
| Category | Index | What EPA says of it |
|---|---|---|
| GoodLevel 1 of 6 · green | 0 to 50 | Air quality is satisfactory, and air pollution poses little or no risk. |
| ModerateLevel 2 of 6 · yellow | 51 to 100 | Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution. |
| Unhealthy for Sensitive GroupsLevel 3 of 6 · orange | 101 to 150 | Members of sensitive groups may experience health effects. The general public is less likely to be affected. |
| UnhealthyLevel 4 of 6 · red | 151 to 200 | Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects. |
| Very UnhealthyLevel 5 of 6 · purple | 201 to 300 | Health alert: The risk of health effects is increased for everyone. |
| HazardousLevel 6 of 6 · maroon | 301 and higher | Health warning of emergency conditions: everyone is more likely to be affected. |
Who EPA means by sensitive groups
It depends on the pollutant. EPA asks agencies to name these groups when a pollutant’s index is above 100:
- Ozone
- People with lung disease, such as asthma; children, including teenagers; people who are active outdoors; and older adults.
- Fine particles (PM2.5) and particles (PM10)
- People with heart or lung disease; older adults; and children, including teenagers. In addition, some minority groups, people with lower incomes, and outdoor workers may experience higher exposure that can worsen underlying health conditions.
- Nitrogen dioxide
- People with lung disease, such as asthma; children, including teenagers; and older adults.
- Carbon monoxide
- People with heart disease.
Where the words come from
The six sentences are the table “AQI Basics for Ozone and Particle Pollution” on airnow.gov. The colours, the sensitive groups and the advice printed with a reading above — what to do at each category, pollutant by pollutant — are Tables 2, 4 and 5 of EPA’s Technical Assistance Document for the Reporting of Daily Air Quality – the Air Quality Index, the May 2026 edition, read on 6 October 2026. They are quoted whole and unchanged. This page is not EPA’s, and it is not medical advice: a person with a heart or lung condition should follow their own clinician’s plan.
AQI Basics on airnow.gov · The Technical Assistance Document
Method
Whose figures, how fresh, and what is not known.
What is read, and how
The readings, the forecasts and the monitors are EPA AirNow’s public file products on files.airnowtech.org, which need no key: the reporting-area file (every area’s current index, its forecasts and yesterday’s peak), the list of ZIP codes with the one reporting area an agency filed each under, and the hourly file of every monitor with its position and its index by pollutant. Together they run to several megabytes, so your browser does not fetch them. A small relay on this site reads them once for every reader, keeps its own index of them, and answers a ZIP code in a few kilobytes. The line under each reading says which source it came from.
The relay can also ask the AirNow web service for the reading and the forecast, and OpenAQ for a wider list of stations, when this site holds a key for either. Both are optional. Without them the page is complete on the public files, and it says which it is reading.
How fresh it is
AirNow rewrites the reporting-area file about twice an hour and publishes each hour’s monitor file twenty to forty-five minutes after that hour ends, revising it for three days as late readings arrive; the minutes vary from hour to hour. The relay checks the area file and the newest hour every ten minutes, the two hours before it hourly, and the ZIP list once a day. So an area’s reading is usually between a quarter of an hour and an hour and a half old when you see it, and a monitor’s between about twenty minutes and two hours; each is printed with its own hour, never as “now”. An area’s stamp is the end of the hour measured, in the area’s own time; a monitor’s is the hour measured, in yours. Where AirNow’s stamp for an area cannot be squared with the state it is in or with that area’s own monitors, the stamp is printed as it came and no age is worked out from it. While this page is open and visible it asks again every ten minutes, and redraws only when the answer has changed.
When a source does not answer
If AirNow is slow, down, limiting requests or sends something that is not its file — a file cut short, or one much shorter than the last — the relay keeps its last good copy and the page prints the reason and the copy’s age beside the figures. A copy more than a day old is not shown at all. If the relay itself cannot be reached, the page keeps the last answer this browser had for the ZIP code, marked with its time. Nothing is filled in: a block with no data says why it is empty.
What the page does not know
The air on your street. A reading is a monitor’s, or the worst of an area’s monitors, and smoke, traffic and terrain change the air over short distances. Distances are straight lines from the centre of the ZIP code, not from your door. The index for ozone and particles is AirNow’s NowCast, which weights recent hours; it is not the 24-hour figure a regulator uses. About fourteen thousand of the Census Bureau’s ZIP areas are not in AirNow’s list at all: for those the page places the ZIP with the Census Bureau’s table, looks for a reporting area within 25 miles and for monitors within 50, and says how far away they are. Such an area’s figures are a neighbour’s and are marked so beside the number; when a reporting monitor stands nearer than that area’s centre, the monitor leads and the neighbour follows. An area AirNow lists but has sent no record for today is said to have none, which is not the same as a file that could not be read. Indoor air, pollen and pollutants outside the index are not here, and low-cost sensors appear only where the OpenAQ upgrade is switched on, as a list of stations and concentrations, never as an index. AirNow’s real-time data are preliminary and unverified; the official record is EPA’s Air Quality System.
Your ZIP code and your location
The ZIP code you type goes to this site’s relay and no further on the public-file route: AirNow is never told which ZIP was asked for. If the site is using the AirNow web service, the ZIP is passed to it by the server, not by your browser; OpenAQ, if in use, is passed the centre of the ZIP code the same way. “Use my location” asks the browser once, only when you press it; the position is rounded to a hundredth of a degree, about a kilometre, before it is sent to the relay, and it is not stored. The model panel is different: your browser asks Open-Meteo directly, for the centre of the ZIP code or the rounded point, so Open-Meteo sees that request. The last ZIP code you asked for, and the relay’s last answer for it, are kept in this browser’s own storage so the page can open on them; nothing is written to the address bar. Like every server, this one logs requests. Questions and corrections: labs@labs.llc.
Every source, and what it asks
- U.S. EPA AirNow and its partner agencies
- Observations, forecasts and monitor data from the AirNow file products (files.airnowtech.org:
reportingarea.dat,cityzipcodes.csv,HourlyAQObs). The data belong to the federal, state, local and tribal air quality agencies that report them, named beside each forecast and monitor; a list is at airnow.gov/partners. Under AirNow’s Data Exchange Guidelines the figures are shown unaltered, in the AQI’s categories and EPA’s colours, and they are preliminary: not fully verified, subject to change, and not for regulatory use. - U.S. EPA, the Air Quality Index
- The category names, ranges, colour formulas, sensitive groups and cautionary statements: airnow.gov’s AQI Basics table and the Technical Assistance Document for the Reporting of Daily Air Quality (May 2026). United States government works.
- U.S. Census Bureau
- The 2020 ZIP Code Tabulation Area gazetteer, public domain: the centre of a ZIP code that AirNow’s list does not carry. Shipped with the site, not fetched. A ZIP with no tabulation area, such as one for post-office boxes only, cannot be placed.
- Open-Meteo and the Copernicus Atmosphere Monitoring Service
- The modelled panel only: Open-Meteo’s Air Quality API, under CC BY 4.0, serving CAMS forecasts (generated using Copernicus Atmosphere Monitoring Service information). Asked by your browser; the US index in that panel is Open-Meteo’s arithmetic on model output, not AirNow’s.
- AirNow web service and OpenAQ, when a key is held
- Optional upgrades the relay uses only if this site’s configuration holds a key: airnowapi.org for the reading and forecast by ZIP code, and OpenAQ for stations within 25 kilometres, credited to OpenAQ and to each station’s own provider. When either is in use the page says so beside the figures.