Qualité de l’air à Yakima

What is the air quality like in Yakima, Washington?

Air quality in Yakima, Washington is primarily challenged by particle pollution (PM2.5), which varies throughout the year with weather, pollution events and the change of seasons.

Yakima’s winter months often bear more than three times the concentration of deadly PM2.5 as summer months. In 2019, November through March represented the most polluted months of the year. All exceeded the US EPA standard for “good.” Clean air in Yakima’s spring and summer, however, have pollution levels low enough to round out an annual air quality average of “good.”

The 2020 State of the Air report, published by the American Lung Association (ALA), found that air quality in Yakima reached a record high for short-term particle pollution during the three years from 2016 to 2019, the most recent monitoring period.¹

The federal government deems counties that average more than the allowable 3.2 unhealthy pollution days for PM2.5 “nonattainment” regions due to the significant risks that exist when breathing unhealthy air quality for days at a time. Yakima County exceeded this standard by more than 5 times in 2016 to 2018 with an average of 17.8 unhealthy PM2.5 days per year. Such frequent unhealthy air caused the region to rank #5 nationally for worst 24-hour PM2.5 out of 217 metropolitan areas included in the report. This represented a significant jump from the previous two monitoring periods, in which Yakima averaged 14.8 (2015 to 2017) and 5 (2014 to 2016) unhealthy PM2.5 days per year.

Short-term PM2.5 particle pollution in recent years has been primarily attributable to wildfires. Wildfires have been increasing in frequency and severity across America’s West. 2017 and 2018 represented record-breaking wildfires seasons, recently topped by 2020. Climate change is attributed to worsening wildfire seasons as warmer temperatures cause earlier snowmelt and longer dry seasons (less rain and humidity). Unsurprisingly, due to the size and nature of wildfires, dense smoke has the propensity to travel great distances and severely impact the air quality of surrounding areas.

Follow Yakima’s live air pollution data presented at the top of this page to stay informed when pollution reaches unhealthy levels. Anything beyond “green” (good) poses some level of risk. When air quality reaches “orange” or “red” levels, follow recommended health advice to reduce your pollution exposure.

What causes air pollution in Yakima?

Emission sources in Yakima include mobile sources (motor vehicles, freight trucks, and farm equipment), stationary sources (industry and manufacturing, agricultural processing plants, and construction equipment), and area sources (wood burning, wind-blown dust, and transboundary air pollution from neighboring cities or regions).

Mobile sources

In the United States, transportation is the largest source of air pollution, comprising roughly half of all emissions.² Car tailpipes output a combination of hazardous air toxins, including half of the carbon monoxide and nitrogen oxides present in our air and almost a quarter of the hydrocarbons and PM2.5.

In Yakima, a city of 91,067 residents with a larger metropolitan area of 243,231, there are fewer passenger vehicles on the road than larger cities. The average commute time here is just 17 minutes compared to the national average of 25.7 minutes.³ On the other hand, only 1.1 percent of Yakima residents use mass transit options compared to the national average of 5.1 percent, and only 3.3 percent work from home compared to the national average of 4.7 percent. Reducing vehicular emissions by promoting hybrid or electric vehicle ownership, mass transit options, and more stringent fuel standards is one opportunity for significantly reducing air pollution levels in Yakima.

The city is already preparing for a cleaner future with the adoption of electric vehicles. Currently, Yakima has just 171 registered electric vehicles (EVs) compared to 42,500 registered EVs across Washington state.⁴ But in 2019, Yakima secured roughly 60,000 dollars in grant money to establish eight additional electric vehicle charging stations. Many of the new stations will be established near Yakima Valley College, which has numerous commuters from neighboring cities.

Stationary sources

Yakima’s mining, logging, agricultural processing, and construction industries represent a majority of the city’s stationary sources. The sources represent a smaller share of the city’s overall emissions, but are growing in terms of jobs and productivity.⁵ Similarly, with mobile emission sources, stationary sources emit as a result of using fossil-fuel combustion for energy. As new technologies and more stringent regulations encourage cleaner energy sources and higher fuel efficiency, emissions from this sector are likely to fall, albeit gradually.

Area sources

The Yakima valley is a productive agricultural region best regarded for its apple, wine, and hop production. It is often counterintuitive that agricultural land contributes to poor air quality. But the use of gas-powered agricultural equipment, spraying of pesticides, processing facilities, and generation of dust all contribute to Yakima air pollution.

The most significant area pollution source in Yakima, however, is domestic wood burning. Winters here are cold. December, for example, averages temperatures below freezing.⁶ During these months, many homes heat with wood stoves and furnaces, which are usually outfitted with relatively poor filters.

Thermal inversions, a weather event common in freezing winters in which ground-level air is cooler than the air directly above it, exacerbate the impact of these emissions by preventing air pollution from dispersing normally. Rather, the higher warm air layer traps polluted air near the ground surface.

Yakima Regional Clean Air Authority has instituted the use of preemptive burn bans during temperature inversions in order to alleviate air pollution levels during Yakima’s winter months.⁷ Still, Yakima’s strong seasonal air pollution prevails, indicating that more must be done in the future to achieve “good” air quality standards during these months.

Is air pollution in Yakima worse than surrounding areas?

Air quality in the Yakima valley tends to suffer from higher pollution levels than surrounding cities, even those cities with significantly larger populations such as Portland and Seattle. The reason for this owes more to the valley’s inland geography and climate, than to the amount of emissions produced in the city.

Yakima is located in a basin between two ridges and high-reaching mountains, including Mount Rainier just 60 miles to the northwest. As warmer air flows over Yakima’s surrounding hills and mountains, it traps cooler air in the valley in a weather event called a subsidence inversion. During these conditions, the airflow acts like a lid over a bowl, causing air pollution in Yakima to accumulate until weather patterns change.

Similarly, Yakima is affected by another type of pollution trapping inversion called a cool air inversion. Winters here are cold: December, the coldest month, averages a temperature of 28.5 degrees (°F). There are 22 days per year, moreover, whose temperatures do not rise above freezing. During these months, there is often snow coverage on the ground. When ground-level air is freezing as a result of snow-coverage or lack of direct sunlight, a thermal inversion can occur in which a warmer air layer traps freezing ground level air below. As with a subsidence inversion, this prevents Yakima’s air pollution from dispersing in the atmosphere. Rather, it accumulates until the weather changes.

Over the last three years, Yakima PM2.5 air pollution levels have averaged 10.4 μg/m³ in 2019; 11.4 μg/m3 in 2018; and 14.6 μg/m3 in 2017. Over the same three years, neighboring metropolitan areas have averaged PM2.5 concentrations (μg/m³) of:

• Portland air quality: 8.1 in 2019; 6.9 in 2018; 7 in 2017.
• Seattle air quality: 7.5 in 2019; 8.3 in 2018; 8.5 in 2017.
• Ellensburg air quality: 6.5 in 2019; 8.2 in 2018; 16.1 in 2017.
• Kennewick air quality: 6.5 μg/m³ in 2019; 8.2 in 2018; 11.7 in 2017.

Where is smoke coming from in Yakima?

Smoke in Yakima is often seasonal, occurring more commonly in the fall with increased wildfire activity and in the winter as a result of domestic wood burning.

In the context of air pollution, “smoke” often refers to visibility-reducing particle pollution, such as airborne ash, soot, and chemicals. Smoke can also include harmful gases, such as carbon monoxide, nitrogen oxides and sulfur dioxide; however, these gases tend to be emitted at levels considered less dangerous for human health than particle pollution.

In 2019, five months (November-March) averaged air quality levels that exceeded the good US AQI standard. November and December were Yakima’s most polluted months, tied with an AQI 71 (moderate).

Use Yakima’s air quality map to locate active fires and watch the flow of PM2.5 emissions in real time. Analyzing this data helps to provide insights into the origins of smoke in Yakima.

When will smoke clear in Yakima?

Air quality is dependent on two primary factors: emissions and weather conditions. The role of emissions on air quality is intuitive, as emissions release air pollutants into the atmosphere. Weather, however, dictates how quickly air pollution disperses and where it will travel.

Even during active wildfires, locations just miles away can experience perfectly clean air quality depending on wind direction, speed, and other weather conditions.

IQAir’s air quality forecast for Yakima Washington uses machine learning to crunch millions of data points in order to analyze how current and past emissions will be affected by a location's geography and weather. The same method is employed for the thousands of global locations on the IQAir platform. Discover Yakima’s forecast air pollution data on the top of this page, beneath the current health recommendations.

+ Article Resources

[1] American Lung Association. (2020). State of the air – 2020.
[2] National Park Service. (2020). Where does air pollution come from?
[3] Best Places. (2020). 2020 Compare Cities Commuting: Yakima, WA.
[4] Frank J. (2019, July 16) Eight electric charging stations coming to YVC. Kima TV.
[5] Meseck D. (2020). Yakima County profile. Employment Security Department.
[6] National Oceanic and Atmospheric Administration. (2020). NowData - NOAA Online Weather Data.
[7] Bain K. (2017, December 13). Yakima can breathe a bit easier despite inversion because of proactive burn ban. Yakima Herald.