Why is the Austin air quality so bad today? Pollution high Thursday

Although the worst air pollution occurs in West Texas and the Houston area, incidents near Austin also affect air quality.

If you opened your phone's weather app to an air quality alert this morning in Austin, you're not alone — apps like the Apple Weather app, AccuWeather and IQAir have deemed the air quality "unhealthy for sensitive groups" Thursday.

Here's what you need to know about the air quality in Austin on Thursday and what exactly makes it unhealthy.

The short answer: pollution.

According to AirNow, a government website sharing air quality data, air quality is essentially graded on an index from zero to 300+, the Environmental Protection Agency's Air Quality Index (AQI). The numbers are calculated by the concentration of five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide and nitrogen dioxide. The numbers coincide with categories: good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy and hazardous. The most extreme category — hazards — indicates emergency conditions, while the least extreme — good — indicates that air pollution poses little or no risk to the public.

Thursday's AQI is well over 100, according to multiple weather sources, meaning it's unhealthy for sensitive groups and experts are encouraging folks to stay indoors as much as possible.

What does PM2.5 air quality mean?

AccuWeather cites PM2.5 as "fine particulate matter," meaning small pollutant particles with a diameter less than 2.5 micrometers. These particles can be inhaled and enter the lungs and bloodstream.

"The most severe impacts are on the lungs and heart," the AccuWeather website reads. "Exposure can result in coughing or difficulty breathing, aggravated asthma, and the development of chronic respiratory disease."

According to experts at McGill University in Canada, PM2.5 is the type of air pollution that kills the most people worldwide. Experts have called for worldwide air quality standards to prevent what they say are "preventable" deaths from inhaling PM2.5 particles.

What type of pollution is in Austin?

According to the American Lung Association, Austin is high-risk for ozone pollution. A 2025 study gave Travis County a failing grade for the number of high ozone days, as well as for average annual particle pollution. The study gave Travis County a "B" grade for 24-hour particle pollution, meaning the area averaged fewer unhealthy air days due to PM2.5 particles. But the bad days outweighed the good ones, earning Travis County an "F" overall for annual particle pollution. The American Lung Association notes that its methodology differs from the EPA's AQI.

Many of Texas' major metropolitan areas also received "F" grades, the data shows.

How to protect yourself in bad air quality

IQAir cites the following tips for unhealthy air quality days:

• Reduce outdoor exercise
• Close windows to avoid dirty air getting indoors
• Wear masks (primarily for sensitive groups)
• Use an air purifier