How to check air quality where you live right now

The fastest way to see air quality in your area is to visit AirNow.gov, run by the EPA. Type your zip code or city name into the search box, and you get a color-coded number called the Air Quality Index (AQI) for your location. The number ranges from 0 to 500, with green (0–50) meaning good air, yellow (51–100) meaning moderate, orange (101–150) meaning unhealthy for sensitive groups, red (151–200) meaning unhealthy, and purple (201+) meaning very unhealthy. The page updates hourly and shows you which pollutants are highest right now — usually ozone or particle pollution.

If you want real-time readings from a monitor closest to your home, PurpleAir.com shows a map of thousands of sensors, many installed by residents and schools rather than government agencies. You can zoom to your neighborhood and see readings from individual devices. These update every few minutes and can be more granular than official EPA monitors, though they measure differently — PurpleAir focuses on fine particles (PM2.5) rather than the full range of pollutants the AQI tracks.

Your phone can also show you this information without visiting a website. Most weather apps include an air quality card; if yours does not, search your phone's app store for "air quality" and read one that covers your region. Many pull data directly from AirNow or similar government sources.

Key Takeaways

  • AirNow.gov is the official EPA source and updates hourly with a single AQI number and pollutant breakdown for any U.S. location.
  • PurpleAir.com shows real-time readings from thousands of neighborhood sensors and updates every few minutes, useful if you want hyperlocal data.
  • The AQI scale runs from 0 (good) to 500+ (very unhealthy), with color coding that tells you at a glance whether the air is safe for outdoor activity.
  • Weather apps on your phone often include air quality cards that pull from these same sources, so you may not need to visit a website.

Understanding what the AQI number means for your health

The AQI number tells you how polluted the air is and who should be concerned. A reading of 0–50 (green) means air quality is satisfactory and outdoor activity is safe for everyone. A reading of 51–100 (yellow, moderate) means unusually sensitive people — children, older adults, and people with asthma or heart disease — may notice effects and should consider limiting outdoor time. A reading of 101–150 (orange, unhealthy for sensitive groups) means those groups should avoid prolonged outdoor activity; the general population is usually unaffected.

Once the AQI hits 151–200 (red, unhealthy), everyone may begin to experience health effects, and sensitive groups should stay indoors. A reading of 201–300 (purple, very unhealthy) means the general public should avoid outdoor activity, and sensitive groups should remain indoors and keep activity levels low. Above 300 (maroon, hazardous) means everyone should avoid outdoor exertion and stay indoors with windows closed.

The pollutant breakdown matters too. If ozone is the main problem, it tends to peak in the afternoon and evening on hot days, so morning outdoor activity may be safer. If particle pollution (PM2.5 or PM10) is high, it can linger all day and penetrate indoors more easily, so you may need to run an air filter or keep windows closed longer.

Checking air quality for multiple locations

If you travel between cities or want to compare air quality across a region, AirNow.gov lets you check as many locations as you need on one visit — just search each zip code separately and note the readings. Some weather apps also let you save multiple locations and swipe between them to see air quality for each.

For a broader view, the EPA's AirData website (aqs.epa.gov/aqsweb) shows historical air quality trends by county and state, though it updates less frequently than AirNow. This is useful if you are considering a move or want to understand whether air quality in your area is improving or worsening over months or years.

What to do when air quality is poor

When the AQI is orange or higher, reduce time outdoors, especially during peak pollution hours. For ozone, that usually means late afternoon and early evening. For particle pollution, any time of day can be unsafe. If you must go outside, wear an N95 or P100 mask — cloth masks and surgical masks do not filter fine particles effectively.

Indoors, keep windows and doors closed, run your air conditioning on recirculate mode (not fresh air intake), and use a HEPA filter in your home if you have one. If you have asthma or heart disease, keep your rescue inhaler or medications with you and consider staying indoors entirely on very unhealthy days. Children and older adults should also stay indoors when the AQI is in the red or purple range.

Why air quality varies by neighborhood

Air quality is not uniform across a city. A monitor downtown may show orange while a neighborhood five miles away shows yellow, because pollution sources — highways, industrial facilities, wildfires — are not evenly distributed. Wind direction and speed also matter: pollution can blow from one area to another within hours. This is why hyperlocal tools like PurpleAir can be useful; they show you the air quality where you actually spend time, not just the official monitor nearest to city hall.

Elevation and geography also play a role. Valleys and low-lying areas can trap pollution, while hilltops and areas with good air circulation often have better air quality. If you live in a valley or near a major highway, your air quality may be worse than the official city reading suggests.

Seasonal patterns and wildfire smoke

Air quality changes with the season. In many regions, summer brings ozone pollution from heat and vehicle emissions. Fall and winter can bring particle pollution from heating and stagnant air. In western states and areas downwind of wildfires, smoke can degrade air quality dramatically during fire season, sometimes for weeks at a time.

When wildfire smoke is present, the AQI can spike to hazardous levels even if no fires are burning nearby. AirNow.gov and most weather apps will note the source of pollution, so you can tell whether the problem is local traffic and industry or distant smoke. Wildfire smoke often clears when wind patterns shift, whereas local pollution tends to be more persistent.

Tools and apps for ongoing monitoring

Beyond AirNow and PurpleAir, several other tools can help you track air quality. IQAir (iqair.com) shows global air quality and lets you set alerts for when the AQI reaches a certain level in your area. BreezoMeter provides hyperlocal forecasts and historical data. Many regional air quality agencies also run their own websites and apps — search "[your state or county] air quality" to find the local source.

If you have smart home devices, some can integrate air quality data and automatically adjust your air filter or close windows when pollution spikes. Check your device's app to see whether this feature is available.

Frequently Asked Questions

Is the air quality reading the same everywhere in my city?

No. Official EPA monitors are usually located at a few points in each city, so readings can vary significantly by neighborhood. PurpleAir and other hyperlocal tools show you air quality closer to where you live, though they may measure slightly differently than official monitors. If you live near a highway or industrial area, your air quality may be worse than the city average.

What does it mean if the AQI is different on different websites?

Different tools measure different things and update at different times. AirNow uses official EPA monitors and updates hourly. PurpleAir measures fine particles (PM2.5) and updates every few minutes. Weather apps may pull from either source or a third-party service. All are roughly accurate, but hyperlocal tools like PurpleAir may show higher readings because they are more sensitive to nearby pollution sources.

Can I predict when air quality will get worse?

AirNow and most air quality apps include a forecast for the next day or two, showing whether the AQI is expected to improve or worsen. These forecasts are based on weather patterns and known pollution sources. During wildfire season, forecasts can change rapidly as fire locations and wind patterns shift.

Do air purifiers actually help when the AQI is high?

HEPA air purifiers can reduce particle pollution indoors, but they work best in a sealed room with windows and doors closed. They do not filter ozone effectively, so on high-ozone days they provide less benefit. Running your air conditioning on recirculate mode (not fresh air intake) is often more effective than a portable air purifier.

Why is the air quality worse some days than others?

Weather drives most day-to-day changes. Heat and stagnant air trap pollution and make ozone worse. Wind clears pollution away. Rain washes particles out of the air. Wildfires, traffic patterns, and industrial activity also affect daily readings. In summer, you often see worse air in the afternoon and evening; in winter, morning and evening can be worse because of temperature inversions that trap cold air near the ground.