Thousands advised to stay indoors in California, Oregon, Arizona

Parts of three states face potentially unhealthy levels of air pollution early Wednesday, a live map from AirNow shows.

The map shows multiple pockets of fine particle (PM2.5) pollution in the “unhealthy” category. In Arizona, the pocket is centered around Payson, while another area is located along the border between California and Oregon, encompassing parts of Red Rock Valley, Butte Valley, Tule Lake National Wildlife Refuge, Langell Valley, Spring Lake Valley, and areas around Klamath Falls.

At these air-quality levels, the Environmental Protection Agency advises that sensitive groups avoid long or intense outdoor activities and consider moving or rescheduling them indoors. The EPA also recommends the remainder of the population to reduce long or intense activities, and to take more breaks during outdoor activities.

Why It Matters

Officials and experts say that deteriorating air quality heightens health risks for vulnerable populations, such as older adults, children and individuals with respiratory illnesses.

What To Know

AirNow—an air quality data resource—is a partnership between the EPA, National Oceanic and Atmospheric Administration, and other agencies.

The Air Quality Index measures air pollution on a scale from 0 to 301 and above:

• 0—50 (Green): Good—Air quality is satisfactory, and air pollution poses little or no risk.
• 51—100 (Yellow): Moderate—Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
• 101—150 (Orange): Unhealthy for Sensitive Groups—Members of sensitive groups may experience health effects. The general public is less likely to be affected.
• 151—200 (Red): Unhealthy—Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.
• 201—300 (Purple): Very Unhealthy—Health alert. The risk of health effects is increased for everyone.
• 301 and higher (Maroon): Hazardous—Health warning of emergency conditions. Everyone is more likely to be affected.

What People Are Saying

The EPA says on its website: “The size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometers in diameter pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream.

“Exposure to such particles can affect both your lungs and your heart. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including:

• premature death in people with heart or lung disease
• nonfatal heart attacks
• irregular heartbeat
• aggravated asthma
• decreased lung function
• increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.

“People with heart or lung diseases, children, older adults, minority populations, and low socioeconomic status populations are the most likely to be affected by particle pollution exposure, either because they are more sensitive or may have higher exposures.”

What Happens Next

AirNow’s map is regularly updated.

Update, 11/12/2025, 5:01 a.m. ET: This article was updated with additional information.