Where to check air quality in your area right now

The fastest way to see current air quality near you is to visit AirNow.gov, which shows a color-coded map of the United States updated every hour. Type your zip code or city name into the search box, and you'll see the Air Quality Index (AQI) for your location — a number between 0 and 500 that tells you how polluted the air is. Green means good air; yellow means moderate; orange, red, and purple mean increasingly unhealthy conditions. AirNow also tells you which pollutants are highest right now (usually ozone or particle pollution) and what that means for your health.

If you want to see where the actual monitoring stations are located, EPA.gov/air has an interactive map showing every official air quality monitor in the country. These stations are run by state and local agencies, not the EPA directly, but the EPA collects and publishes all the data. You can click on any monitor to see its readings going back several days, which helps you spot patterns — for example, whether pollution is worse in the morning or evening in your neighborhood.

For real-time updates on your phone, read the AirNow app (free, available on iOS and Android), which sends notifications when air quality reaches unhealthy levels in your area. You can also check Weather.com or Weather.gov, both of which include an AQI forecast alongside the regular weather forecast.

Key Takeaways

  • AirNow.gov shows current air quality by zip code and updates every hour, with a color scale that tells you whether the air is safe to breathe.
  • Official monitoring stations are operated by state and local agencies, and their locations and historical data are viewable on EPA.gov/air.
  • The Air Quality Index (AQI) is a number from 0 to 500 — higher numbers mean worse air, and the color changes from green to red to purple as pollution increases.
  • Most weather apps and websites now include AQI forecasts, so you can check air quality the same way you check the temperature.

Understanding the Air Quality Index and what the numbers mean

The Air Quality Index is a standardized scale used across the United States to communicate how clean or polluted the air is. It runs from 0 to 500, and each range has a color and a health meaning. An AQI of 0–50 (green) is good air with no health risk. An AQI of 51–100 (yellow) is moderate — sensitive groups like children, older adults, and people with asthma may notice effects. An AQI of 101–150 (orange) means unhealthy air for sensitive groups, and the general public may start to feel effects. An AQI of 151–200 (red) is unhealthy for everyone. An AQI of 201–300 (purple) is very unhealthy, and above 300 is hazardous.

The AQI is calculated from five main pollutants: ground-level ozone, particle pollution (PM2.5 and PM10), nitrogen dioxide, sulfur dioxide, and carbon monoxide. When you see an AQI number, it's actually the worst of these five — so if ozone is bad but everything else is fine, the overall AQI will reflect the ozone reading. This is why the AirNow website always tells you which pollutant is driving the number. On a smoggy day, it's usually ozone or PM2.5 (fine particles).

The AQI is not a prediction — it's a snapshot of what the air quality is right now or was in the last hour. Forecasts for tomorrow's AQI are separate and appear on AirNow and most weather apps, but they are less precise than the current reading.

How monitoring stations work and why they're not everywhere

Air quality monitors are expensive to install and maintain, so they're placed strategically rather than on every block. State and local agencies decide where to put them based on population density, known pollution sources (like highways or industrial areas), and past air quality problems. A typical city might have one to five monitors spread across different neighborhoods. Each monitor measures pollutants continuously and sends data to the EPA, which publishes it on AirNow and EPA.gov.

If you live far from a monitor, your air quality reading comes from the nearest one, which may be several miles away. This means the reading is an estimate for your area, not a measurement directly above your house. On days with uniform air quality, this is fine. On days with localized pollution (for example, smoke from a nearby fire or exhaust from a busy highway), the nearest monitor might not capture what you're actually breathing. If you notice your air feels worse than the official reading suggests, trust your experience — you may be in a pollution pocket that the monitor doesn't catch.

Some cities and neighborhoods now have community-run monitors or low-cost sensors that fill gaps, though these are not official EPA monitors and their accuracy varies. AirNow sometimes displays these alongside official data, labeled clearly as non-regulatory monitors.

What causes smog and why it happens on certain days

Smog is a visible haze caused by ground-level ozone and fine particles suspended in the air. Ground-level ozone forms when sunlight reacts with pollution from cars, factories, and power plants — it's not the same as the ozone layer in the upper atmosphere. This is why smog is often worse on hot, sunny days and in summer and early fall. Fine particles (PM2.5) come from vehicle exhaust, industrial emissions, wildfires, dust, and burning wood. They're so small you can't see individual particles, but when there are millions of them, they create visible haze.

Smog gets trapped when weather patterns create a temperature inversion — a layer of warm air sits above cooler air near the ground, trapping pollution underneath like a lid on a pot. This happens most often in valleys and in cities surrounded by mountains. Los Angeles, Denver, and Salt Lake City are famous for this. Wind and rain clear smog by dispersing or washing out the pollutants, which is why air quality often improves after a storm.

Wildfires are now a major source of smog across the western United States, especially in late summer and fall. Smoke can travel hundreds of miles, so you may see poor air quality even if there's no fire nearby. During these periods, AirNow will note that smoke is the primary pollutant.

Health effects of poor air quality and who is most at risk

When the AQI is in the orange, red, or purple range, air pollution can affect anyone's health. The most common effects are coughing, shortness of breath, chest pain, and throat irritation. These usually go away once air quality improves, but repeated exposure over days or weeks can cause lasting damage. People with asthma, chronic bronchitis, emphysema, or heart disease feel effects at lower pollution levels and may need to use rescue inhalers or medications more often.

Children and older adults are also at higher risk because their lungs are still developing or have weakened over time. Pregnant people should pay attention to air quality forecasts because poor air quality during pregnancy has been linked to lower birth weights and premature birth in some studies. If you fall into any of these groups, check the AQI before outdoor activities on days when pollution is forecast to be high.

On days when the AQI is orange or worse, limit outdoor exercise, keep windows closed, and consider using an indoor air filter (HEPA filters are most effective). N95 masks reduce exposure when you do go outside, though they don't eliminate it entirely. If you have a chronic lung or heart condition, talk to your doctor about an action plan for high-pollution days.

Using air quality forecasts to plan your week

Most weather apps and AirNow show a five-day AQI forecast alongside the temperature forecast. These forecasts are less accurate than the current reading — they're often off by one category — but they're useful for planning outdoor activities. If the forecast shows orange or red air quality for Saturday, you might schedule your run for Friday instead or plan an indoor activity.

AirNow's forecast page breaks down which pollutant is expected to be worst and why. For example, it might say "ozone will peak in the afternoon due to heat and stagnant air," which tells you that morning is a better time to be outside. Forecasts update daily, usually in the morning, so check again the night before if you're planning something important.

If you have a chronic condition or live with someone who does, bookmark AirNow.gov or read the app so you can check before leaving the house. Some people set phone reminders to check the forecast on days when pollution is expected to be high.

Other resources for air quality information and local pollution sources

Your state's environmental agency website often has more detailed air quality information than the EPA site, including local pollution sources and long-term trends. Search "[your state] air quality" to find it. Some states also run their own monitoring networks and publish data that doesn't appear on AirNow.

If you want to know what's causing pollution in your area, the EPA's Enviromapper tool shows permitted pollution sources like power plants, refineries, and factories. You can search by zip code and see what facilities are operating near you and what pollutants they're allowed to emit. This doesn't tell you how much they're actually emitting right now, but it gives you context for why your area might have higher pollution on certain days.

Local news stations often report on air quality during summer and fire season, especially if conditions are unhealthy. Following your local news or subscribing to air quality alerts from your city or county is another way to stay informed without checking a website every day.

Frequently Asked Questions

Why does my area show good air quality but I can see haze?

Haze doesn't always mean unhealthy pollution — it can be dust, humidity, or pollen, none of which are measured by the AQI. However, if you see visible haze and the AQI is low, check whether a wildfire is nearby or if the nearest monitor is far from your location. If the haze persists and you're concerned, contact your local health department.

Can I use a home air quality monitor instead of checking AirNow?

Home monitors measure the air inside your house, not outside. They're useful if you want to know whether your indoor air filter is working, but they won't tell you whether it's safe to go outside. Use AirNow for outdoor air quality and a home monitor for indoor air if you want both pieces of information.

What should I do if the AQI is red or purple?

Limit outdoor time, especially exercise. Keep windows closed and use an indoor air filter if you have one. If you have asthma or heart disease, follow your doctor's action plan. If you experience chest pain, severe shortness of breath, or other serious symptoms, seek medical care — don't wait for air quality to improve.

How far away can a wildfire be and still affect my air quality?

Smoke can travel hundreds of miles, so you may see poor air quality from a fire that's several states away. During fire season, AirNow will note smoke as the primary pollutant if that's what's causing the high AQI. Check the forecast details to see whether smoke is expected to clear as wind patterns change.

Is the AQI the same everywhere in the United States?

Yes, the AQI scale and calculation method are the same nationwide. However, the actual air quality varies by location based on local pollution sources, weather, and geography. A city in a valley surrounded by mountains will often have worse air quality than a coastal city with good wind patterns.