Las Vegas Air quality today

What is ozone, and why does it build up over Las Vegas?

Ground-level ozone is a colorless gas that can harm health ^[8]. It forms when two kinds of pollution, volatile organic compounds and nitrogen oxides, react in sunlight ^[8]. These come from vehicles, industries, power plants, and products such as solvents and paints ^[8].

Clark County's air quality division says ozone builds up in the Las Vegas Valley during the hottest months ^[5]. Heat, sunlight, gasoline and chemical vapors, vehicle pollution, wildfires and pollution carried in from other places all play a part ^[5]. In 2025, a county meteorologist said the mountains around the valley make it a perfect bowl for ozone to cook ^[5].

Does all of Las Vegas's ozone come from Las Vegas?

No. A 2017 field study reported by NOAA's Chemical Sciences Laboratory looked at ozone from outside the region ^[4]. One source was ozone-rich air pulled down from the stratosphere, the high layer of the atmosphere ^[4]. Another was pollution from Asia, carried across the Pacific Ocean and often mixed with that air ^[4]. Researchers also studied ozone carried in near the ground from California ^[4].

The study found that ozone from outside the region added about 50 to 55 parts per billion to the city's ozone in spring and early summer ^[4]. That is about 70 to 80 percent of the federal ozone limit of 70 parts per billion ^[4]. Layers of ozone sat above the city on more than 75 percent of the days sampled ^[4].

This outside ozone fades in July and August, when ozone made from the city's own pollution is at its highest ^[4]. The researchers said high ozone days later in the summer cannot really be blamed on air from the stratosphere ^[4].

How does wildfire smoke affect Las Vegas's air?

Smoke from wildfires can drift into Southern Nevada ^[5]. It adds tiny particles to the air and can also add to ozone ^[5]. Clark County says wildfires across the western US have become more frequent in summer ^[5]. The NOAA study also saw the effects of regional wildfires on several days in 2017 ^[4].

The county counted 18 days above the federal ozone standard in 2023 and 26 days in 2024 ^[5]. It said wildfire smoke was one cause of the 2024 total, but not the only one ^[5].

In 2021, Clark County asked the EPA to set aside some high ozone days from 2018 and 2020, including days it linked to wildfires in June of both years ^[3]. The EPA did not agree, finding the county had not clearly shown that the fires caused those high readings ^[3].

What about blowing dust?

Dust is a long-running problem in the valley. It is measured as PM10, particles 10 micrometers across or smaller ^[6]. In 1993, the EPA classed the Las Vegas Valley as a serious problem area for PM10 ^[6]. The EPA-approved plan named the main sources as disturbed vacant land, unpaved parking lots, construction, paved and unpaved roads, and race tracks ^[6].

Clark County wrote a set of dust rules for open land and vacant lots, unpaved roads, storage yards, paved roads and street sweeping, and construction ^[6]. One rule covers permits and dust control for construction work ^[6]. The EPA called these rules the backbone of the plan that cleaned up the valley's dust ^[6].

In 2010, the EPA found the valley had met the federal PM10 standard by the end of 2006 ^[6]. Two high readings in July 2011 were set aside because high winds caused them ^[6]. The EPA declared the area clean for PM10 in October 2014, and it stays under a plan to keep it that way ^[7].

How does Las Vegas compare with other US cities?

In the American Lung Association's 2026 State of the Air report, based on 2022 to 2024 data, Las Vegas-Henderson ranked 11th worst in the US for ozone ^[1]. Clark County averaged 22.3 unhealthy ozone days a year and got an F grade ^[1]. In the 2025 report, the area ranked 12th worst ^[1].

For short spikes in particle pollution, the area ranked 31st worst, with 5 unhealthy days a year and an F grade ^[1]. For year-round particle levels, Clark County passed, with levels below the federal standard ^[1].

What is Las Vegas's federal ozone status?

In October 2015, the EPA set the federal ozone limit at 0.070 parts per million ^[2]. An area meets it when the three-year average of each year's fourth-highest daily eight-hour ozone level stays at or below that figure ^[2].

In August 2018, the EPA named the Las Vegas part of Clark County a marginal nonattainment area, meaning it did not meet the limit ^[3]. It missed the 2021 deadline and was moved up to moderate in January 2023 ^[2]. Its figure for 2021 to 2023 was 0.074 parts per million, above the limit, so it missed the August 2024 deadline too ^[2]. In January 2025, the area moved up to serious, with a deadline of August 3, 2027 ^[2][7].

How to protect yourself in Las Vegas

Check the Air Quality Index, or AQI, before planning time outside, and watch for Ozone Action Days ^[8]. Ozone is usually worse in the afternoon and early evening, so plan outdoor activities for the morning ^[8]. When the AQI is unhealthy, choose a less intense activity, take more breaks, or move your activity indoors, where ozone levels are usually lower ^[8].

People most at risk from ozone include people with lung disease such as asthma, children and teenagers, older adults, and people who are active outdoors, including outdoor workers ^[8]. People with asthma should follow their asthma action plan ^[8]. In extreme heat, staying inside with the windows closed and no air conditioning may be dangerous; go somewhere with air conditioning or find a local cooling center ^[8].

When you can see or smell wildfire smoke, Clark County advises staying indoors when you can, keeping windows and doors shut, running the air conditioner, and replacing dirty air filters ^[5].