Finding current smog and air quality information for your location
You can check smog and air quality near you right now using free government tools that update throughout the day. The EPA AirNow website (airnow.gov) shows real-time air quality data for your zip code or city, and the same information appears on the EPA's mobile app. You enter your location once and see the current Air Quality Index (AQI) — a number that tells you whether the air is good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, or hazardous.
Another option is the National Weather Service, which includes air quality forecasts alongside weather forecasts for your area. Many local news stations also display air quality on their websites and weather apps. If you live near a major city, your city or county health department often runs its own air monitoring network and publishes readings on their website — these are sometimes more detailed than the national averages.
Key Takeaways
- The EPA AirNow website and app show real-time air quality for any U.S. zip code and update several times per day.
- The Air Quality Index (AQI) number tells you whether air is safe to breathe outdoors, with different risk levels for children, older adults, and people with lung or heart conditions.
- Local health departments and city websites often publish more detailed air quality readings specific to your neighborhood than national averages do.
- Air quality forecasts help you plan outdoor activities in advance, especially if you have asthma, heart disease, or other conditions affected by poor air.
Understanding the Air Quality Index (AQI) number
The AQI is a single number between 0 and 500 that summarizes how clean or polluted the air is. The EPA color-codes these ranges so you can see at a glance whether conditions are safe. An AQI of 0–50 (green) means air quality is good. An AQI of 51–100 (yellow) is moderate — most people can be outdoors, but people with asthma or heart disease may notice symptoms. An AQI of 101–150 (orange) means the air is unhealthy for sensitive groups, and children, older adults, and people with respiratory or heart conditions should limit outdoor activity.
An AQI of 151–200 (red) is unhealthy for the general population — everyone should reduce prolonged outdoor exertion. An AQI of 201–300 (purple) is very unhealthy, and most people should avoid outdoor activity. An AQI above 300 (maroon) is hazardous, and everyone should stay indoors. The AQI measures five main pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), nitrogen dioxide, sulfur dioxide, and carbon monoxide. The number you see is based on whichever pollutant is worst that day.
Where smog comes from and why it changes daily
Smog forms when sunlight reacts with nitrogen oxides and volatile organic compounds released by cars, factories, power plants, and other sources. This type of smog — called ozone smog or photochemical smog — is worst on hot, sunny days with little wind, because heat and sunlight speed up the chemical reaction. Particulate smog, made of tiny dust and soot particles, can come from wildfires, dust storms, industrial emissions, or vehicle exhaust, and it can linger even on cloudy days.
Air quality changes from hour to hour and day to day depending on weather, traffic patterns, and industrial activity. Morning rush hour often brings a spike in pollution. Afternoon heat can worsen ozone smog. Wind pushes pollution away or traps it in valleys. Wildfires hundreds of miles away can send smoke into your area. This is why checking the current reading and the forecast before you plan outdoor activities matters more than remembering yesterday's number.
Using air quality forecasts to plan your week
The EPA AirNow website includes a forecast for the next day, and many local air quality agencies publish forecasts three to five days ahead. These forecasts help you schedule outdoor exercise, yard work, or children's sports on days when air quality will be better. If you have asthma, heart disease, or another condition sensitive to air pollution, checking the forecast lets you prepare — you might use your rescue inhaler before going outside on a high-pollution day, or you might move an outdoor activity to a cleaner day.
Forecasts are less precise than current readings because weather and pollution sources are unpredictable, but they give you enough information to make decisions. If the forecast shows unhealthy air for several days, you can plan indoor activities instead. If you see a spike coming, you can stock up on groceries or medications before the air gets bad, rather than having to go out during peak pollution hours.
Protecting yourself when air quality is poor
When the AQI is in the orange, red, or purple range, limit time outdoors, especially during peak pollution hours — usually late morning through early evening when ozone is highest. If you must go outside, wear an N95 or P100 mask, which filters out particulate pollution. Cloth masks and surgical masks do not filter air effectively enough to protect against smog. Keep windows and doors closed on high-pollution days, and use an air conditioner set to recirculate indoor air rather than drawing in outside air.
If you have asthma, heart disease, or lung disease, talk to your doctor about your personal risk level and what precautions make sense for you. Some people need to stay indoors on days when others can still go outside. Keep rescue medications on hand and know the early signs that pollution is affecting you — shortness of breath, chest tightness, or wheezing — so you can move indoors before symptoms get worse. Children and older adults are also more vulnerable, so watch them closely on high-pollution days.
Getting alerts when air quality drops
The EPA AirNow app lets you set up notifications so you receive a message when air quality reaches a level you choose. You can set alerts for your home location, your workplace, or anywhere else you spend time regularly. Many local health departments and air quality agencies also send email or text alerts when pollution reaches unhealthy levels. Check your city or county health department website to see whether they offer this service and how to sign up.
Some weather apps and smart home devices also include air quality alerts. If you use a weather app, check whether it has an air quality feature and whether you can customize the alert threshold. Having alerts set up means you do not have to remember to check the website every day — you will know when conditions change enough to affect your plans or your health.
Finding detailed air quality data for your specific neighborhood
The EPA AirNow map shows data from official monitoring stations, which are usually located in central areas of cities or counties. If you live in a neighborhood far from a monitoring station, the reading you see may not reflect conditions exactly where you are — pollution can be worse near highways, industrial areas, or ports, and cleaner in residential neighborhoods upwind. To find more granular data, check your local air quality agency's website. Many cities and counties run additional monitoring stations and publish readings by neighborhood or district.
Some universities and research organizations also run air quality monitoring networks and publish data online. If you live near a major source of pollution — a highway, airport, refinery, or power plant — your local health department may have specific information about air quality in that area. Calling your city or county health department and asking whether they have neighborhood-level data is often faster than searching online.
Frequently Asked Questions
Is the air quality reading the same everywhere in my city?
No. Official monitoring stations are usually in central locations, so readings may not match conditions in your neighborhood. Pollution is often worse near highways, ports, and industrial areas, and cleaner in residential neighborhoods upwind. Your local health department may publish neighborhood-level data if you ask.
Can I trust the air quality forecast?
Forecasts are less accurate than current readings because weather and pollution sources change unpredictably. They are useful for planning a few days ahead, but check the current reading before you go outside. A forecast showing poor air tomorrow does not mean today's air is bad.
What does PM2.5 mean?
PM2.5 refers to particulate matter smaller than 2.5 micrometers — tiny particles that can lodge deep in your lungs. It comes from vehicle exhaust, wildfires, dust, and industrial emissions. The AQI includes PM2.5 as one of the five pollutants it measures.
Do I need a special mask to protect against smog?
Yes. N95 and P100 masks filter particulate pollution effectively. Cloth masks and surgical masks do not filter air well enough to protect against smog. Make sure the mask fits snugly so air does not leak around the edges.
Why is air quality worse on some days than others?
Heat, sunlight, wind, and traffic patterns all affect pollution levels. Hot, sunny days with little wind trap pollution and speed up chemical reactions that create ozone smog. Morning rush hour often brings spikes. Wind pushes pollution away or traps it in valleys depending on direction.