Where to find real-time smog and air quality data for your location

The fastest way to check smog near you is the AirNow website (airnow.gov), which shows the Air Quality Index (AQI) for your zip code updated every hour. Type in your location and you'll see the current air quality color-coded from green (good) to maroon (hazardous), plus which pollutants are highest right now — usually ozone or particulate matter.

Your phone also has built-in options. Apple Weather and Google Weather both display AQI in the hourly forecast if you enable it in settings. The EPA's official AirNow app works on iOS and Android and sends alerts when air quality drops below a threshold you set.

If you want hyperlocal data, some cities run their own monitoring stations. Search "[your city name] air quality" to see if your local health department or environmental agency publishes readings from stations closer to your neighborhood than the nearest AirNow monitor.

Key Takeaways

  • AirNow.gov shows your local AQI updated hourly and is free to use without creating an account.
  • The AQI number tells you how polluted the air is; above 100 means sensitive groups should limit outdoor time.
  • Your phone's built-in weather app can display AQI if you turn it on in settings.
  • Some cities publish their own air quality data from local monitoring stations, which may be more precise for your neighborhood.

Understanding the Air Quality Index (AQI) number

The AQI is a single number from 0 to 500 that tells you how clean or polluted the air is. Each range has a color and a health meaning. Green (0–50) is good; yellow (51–100) is moderate and means sensitive people should think about limiting outdoor time; orange (101–150) means members of sensitive groups should avoid prolonged outdoor activity; red (151–200) means the general public may start to feel effects; purple (201–300) is very unhealthy; and maroon (301+) is hazardous.

Sensitive groups include children, older adults, and people with asthma, heart disease, or lung disease. If you're in one of these groups and the AQI is orange or higher, outdoor exercise and time outside should be limited or moved indoors.

The AQI focuses on five main pollutants: ground-level ozone (smog), particulate matter (PM2.5 and PM10), nitrogen dioxide, sulfur dioxide, and carbon monoxide. AirNow tells you which one is driving the number, so you know whether you're dealing with smog from car exhaust and industry or smoke from wildfires.

Why smog happens and when it's worst

Smog forms when sunlight reacts with nitrogen oxides and volatile organic compounds released by cars, factories, and power plants. This is why smog is often worst in the afternoon and early evening, when the sun is strongest and traffic is heavy. Temperature inversions — when a layer of warm air traps cooler air below it — can trap smog close to the ground for days.

Smog is seasonal. In most of the United States, it peaks in summer and early fall when temperatures are high. In some regions, winter inversions can also create smog problems. Wildfires add another layer: smoke from fires hundreds of miles away can drift into your area and spike the AQI even if local sources are quiet.

What to do when smog is high

When the AQI is orange (101–150) or higher, limit time outdoors, especially strenuous outdoor activity. If you must go outside, an N95 or P100 mask can reduce the amount of pollutants you breathe in, though it won't eliminate exposure. Masks work best when they fit snugly and you're not exercising hard — the effort of breathing through a mask during a run can sometimes be counterproductive.

Indoors, close windows and doors to keep outdoor air out. If you have an air conditioner, run it on recirculate mode rather than bringing in outside air. HEPA filters in home air purifiers can remove some particulate matter, though they won't remove gases like ozone. Keep inhalers and medications on hand if you have asthma or heart disease.

Check the forecast for the next few days. Many weather services now include AQI forecasts, so you can plan outdoor activities for days when air quality is better. If you work outdoors or exercise regularly, building this into your routine can reduce your exposure over time.

Free tools and apps beyond AirNow

BreezoMeter (breezometer.com) shows AQI and breaks down which specific pollutants are high, plus forecasts for the next few days. IQAir (iqair.com) displays real-time data from thousands of monitors worldwide and includes health recommendations based on your AQI level. Both are free to use on the web or as apps.

Purple Air (purpleair.com) crowdsources air quality data from personal monitors installed by residents and businesses. This can show you hyperlocal variation — one neighborhood might have cleaner air than another a few miles away. The trade-off is that Purple Air monitors are less standardized than official EPA monitors, so readings can vary.

If you want to track trends over time, the EPA's historical data tool lets you read AQI readings by location and date going back years. This is useful if you're deciding whether to move or want to document long-term air quality patterns in your area.

How smog affects your health

Short-term exposure to high smog levels can cause coughing, throat irritation, chest pain, and shortness of breath, even in healthy people. Long-term exposure — living in a smoggy area for years — is linked to reduced lung function, asthma development, and increased risk of heart disease and early death.

Children are more vulnerable because their lungs are still developing and they spend more time outdoors. Older adults and people with existing heart or lung disease face higher risk of serious effects. Even if you don't feel symptoms, smog is still affecting your lungs and cardiovascular system.

If you live in an area with frequent high AQI days, reducing your exposure where you can — limiting outdoor time on bad days, using air filters indoors, or considering a move to a cleaner area if feasible — can lower your long-term health risk.

Frequently Asked Questions

Is an AQI of 100 safe?

An AQI of 100 is at the boundary between moderate and unhealthy for sensitive groups. Healthy adults can usually tolerate it, but children, older adults, and people with asthma or heart disease should limit outdoor time and strenuous activity. If you're in a sensitive group, treat 100 as a signal to stay indoors or reduce outdoor exertion.

Can I trust the AQI if it seems wrong for my area?

Official AirNow monitors are accurate, but they're not everywhere — your nearest monitor might be miles away. Local wind patterns, nearby highways, or industrial sites can make your actual air quality different from the reported number. If you consistently notice a difference, check whether a local agency publishes data from monitors closer to you, or consider a personal air quality monitor.

Do air purifiers actually work?

HEPA air purifiers remove particulate matter (dust, pollen, some wildfire smoke) but not gases like ozone. They work best in a single room with the door closed. They're most useful during high AQI events if you spend a lot of time in one room, but they're not a substitute for staying indoors when smog is bad.

Why does my area have high AQI but I can't see smog?

Smog isn't always visible. Ground-level ozone, which is a major component of smog, is colorless. You might have unhealthy air quality without seeing a brown haze. This is why checking the AQI number matters more than what you see outside.

How far away can wildfire smoke travel?

Wildfire smoke can travel hundreds of miles and spike AQI for days or weeks. Smoke from fires in the West can reach the East Coast. If your AQI suddenly spikes and there are no local fires, check whether wildfires are burning upwind of you. The AirNow website and local news usually identify whether high AQI is from local smog or distant smoke.