|2||Seeley Lake, Montana|
|3||Hot Sulphur Springs, Colorado|
|4||Mono Vista, California|
|5||Peaceful Valley, Washington|
|6||Tuolumne City, California|
|8||Klamath Falls, Oregon|
|9||Las Vegas, New Mexico|
|10||Live Oak, California|
(local time)SEE WORLD AQI RANKING
8:13, Mar 3
live AQI index
|Air pollution level||Air quality index||Main pollutant|
|Good|| 39 US AQI||PM2.5|
|PM2.5|| 9.5 µg/m³|
|pm10|| 35.8 µg/m³|
|o3|| 32 µg/m³|
|so2|| 2.6 µg/m³|
|co|| 458 µg/m³|
|Open your windows to bring clean, fresh air indoors|
|Enjoy outdoor activities|
|Saturday, Feb 27|
Good 34 US AQI
|Sunday, Feb 28|
Good 25 US AQI
|Monday, Mar 1|
Good 35 US AQI
|Tuesday, Mar 2|
Good 31 US AQI
Good 20 US AQI
|Thursday, Mar 4|
Good 24 US AQI
|Friday, Mar 5|
Good 25 US AQI
|Saturday, Mar 6|
Good 25 US AQI
|Sunday, Mar 7|
Good 19 US AQI
|Monday, Mar 8|
Good 17 US AQI
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Phoenix’s air quality on average is rated an air quality index (AQI) score of less than 50, or “good.” Despite Phoenix's clean air quality on annual and monthly averages, the city still experiences a number of unhealthy ozone and PM2.5 days. From 2016 to 2018, there was a weighted average of 46.5 days of unhealthy air.1 These pollution days resulted in Phoenix failing air pollution attainment for ozone and PM2.5.
Phoenix tends to experience cleaner air in the summer and more polluted air in the winter. Temperature inversions in the winter largely contribute to these months having a 2.5 times higher AQI than in the summer months. On average, May and June are Phoenix's cleanest months annually, while December and November are the most polluted.
The greatest challenge to Phoenix air quality is ozone pollution. Ozone is a gas pollutant formed when nitrogen oxides and organic substances react under sunlight. Since ozone is not released directly but rather formed in the atmosphere from other pollutants, it is often considered a difficult pollutant to control.
Abundant sunlight and heat as a requirement for ozone formation means that Phoenix ozone levels tend to be worse in the summer than in the winter (an opposite trend from Phoenix average pollution levels and PM2.5 levels). In 2019, unhealthy ozone levels only occurred between the dates of May 3 and September 13.1 Historically, ozone levels are always in the “green” healthy category during the winter months.
According to the State of the Air report published by the American Lung Association, Maricopa County, of which Phoenix is the county seat, was rated an “F” and ranked 7th among 228 included metropolitan areas for high ozone days.1 From 2016 to 2018, there was a weighted average of 39.8 days that were deemed unhealthy for ozone alone.
While Phoenix continues to struggle to meet current ozone standards, many health experts are proponents for further lowering the federal standard. They advocate that current regulations limiting ozone levels to no more than 70 ppb do not sufficiently safeguard the most vulnerable populations for adverse health effects.3 In order for Phoenix to meet current standards and strive for even lower levels, the city must focus on its greatest ozone contributor: transportation.
Phoenix live air quality data is available at the top of this page. Follow Phoenix forecast air quality data and the posted health advisories to take action against pollution levels and reduce your pollution exposure.
Phoenix, along with much of the United States, experienced significant air quality improvements since the Clean Air Act of 1970 and later 1990 amendments.
In recent years, however, Phoenix air quality has been on the decline for both PM2.5 and ozone pollution. 2019 was an exception to this trend, showing improvements as compared to both 2018 and 2017.
For PM2.5 pollution, for example, Phoenix experienced an annual average of 8.4 μg/m3 in 2017 and 8.6 μg/m3 in 2018 (a small 2.4% increase from year to year). In 2019, meanwhile, PM2.5 levels dropped 32.6% to 5.8 μg/m3, the lowest annual average since at least 2002.
For ozone pollution, Phoenix experienced 34 days of air exceeding the Clean Air Act standard for ozone (70 ppb) in 2016, 48 days in 2017, and 55 days in 2018. 2019, on the other hand, showed an improvement, with only 40 days above the federal standard.2
Even with a decrease in ozone pollution in 2019, ozone levels still pose significant risks to Phoenix residents. Containing ozone levels in the future relies primarily on reducing auto emissions rather than emissions from Phoenix’s relatively small manufacturing sector.4 Transportation emissions can be further reduced by shifting to more fuel-efficient, low emission vehicles and making public transportation more accessible and attractive. According to a study by the South West Energy Efficiency Project (SWEEP), moving to electric vehicles could greatly reduce Arizona air pollution levels, with reductions in nitrogen oxide (a key precursor pollutant for ozone formation) levels by up to 76%, and PM2.5 levels by up to 60%.5
Phoenix’s unhealthy air pollution is largely the result of transport emissions and industry. Seasonal weather effects, meanwhile, play an important role as these effects can prevent polluted air from dispersing normally.
The accumulation of air pollution in Phoenix during the winter, for example, is primarily the result of temperature inversions. In normal conditions, the sun heats the ground creating warmer air near the ground’s surface and cooler air just above. In these conditions, polluted ground level air is able to rise and disperse over large areas. During a temperature inversion, generally occurring in the winter, weak sunlight and colder conditions create colder ground level air and warmer air above. When this happens, the cold polluted air near the surface is trapped or prevented from rising due to the warm air above. The result is the accumulation of pollution over time as emissions remain relatively constant, often creating a ‘brown haze’ over the horizon.
Local winds can further exacerbate this effect by moving pollution across different parts of the valley.6 During the day, pollution spreads more freely across the valley, moving up the mountains and to the surrounding Phoenix metropolitan area. At night, as temperatures drop, cold air flows from the mountains to the south, settling in the lowest point of the valley. This moving air contains pollutants from the surrounding area, concentrating them near the southern part of the Salt River and west Phoenix.
When a temperature inversion is in place, only rain or wind can diffuse the cold, polluted air. Heat and sunlight during the afternoon can end an inversion, allowing pollution to disperse, but in the winter, inversions frequently occur again a few hours after dusk.
Warming summer temperatures as a result of global warming may be worsening Phoenix's ozone problem by creating more ideal conditions for ozone formation. Between 1980 and 2015, statewide temperatures have risen from an average 71.3°F to 75.5°F.7 Phoenix is the fourth fastest-warming city in the United States.
Phoenix AQI varies across the city and is usually higher near major roadways. In the winter, west Phoenix often shows slightly higher air quality levels as a result of seasonal weather effects. Use the Phoenix air pollution map to observe the impact of local emission sources on real-time air quality levels, and compare air quality levels to Tucson, Arizona’s second most polluted city after Phoenix.
+ Article Resources
 American Lung Association. (2019). State of the air – 2019.
 Arizona Department of Environmental Quality. (2020). Air quality year-to-date report.
 BMJ. (2020, February 10). Daily exposure to ozone pollution linked to increased risk of death.
 Francis S. (2019, October 27). Arizona's air quality is getting worse and making people sick. Here's how we solve it.
 Salisbury M. (2013) Air quality and economic benefits of electric vehicles in Arizona.
 Stone E. (2019, December 31,). Winter air really is worse in south, west Phoenix. Here's why.
 Climate Central. (2019). American warming: The fastest-warming cities and states in the U.S.
Data sources 4