Data: EPA AirNow, FEMA National Risk Index Last verified: 2026-05-03

What is AQI?

The Air Quality Index (AQI) is a standardized scale from 0 to 500 that measures air pollution levels. 0-50 is "Good," 51-100 is "Moderate," 101-150 is "Unhealthy for Sensitive Groups," and above 150 is "Unhealthy" for everyone. AQI tracks five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Mount Vernon's average AQI of 15 falls in the "Good" range.

Air Quality by ZIP Code in Mount Vernon

AQI varies across Mount Vernon's 2 ZIP codes based on proximity to pollution sources and local geography.

ZIP Code	AQI	Category	Wildfire	Mold
98273	15	Good	17	56	View report →
98274	15	Good	23	44	View report →

Air Quality Overview

Mount Vernon, Washington has good air quality with an average AQI of 15. This means air pollution poses little or no risk. The dominant pollutant measured is PM2.5.

The Air Quality Index (AQI) is an EPA-standardized scale from 0 to 500. Values below 50 are "Good," 51-100 "Moderate," 101-150 "Unhealthy for Sensitive Groups," 151-200 "Unhealthy," 201-300 "Very Unhealthy," and above 300 "Hazardous."

Dominant Pollutant: PM2.5

PM2.5 (fine particulate matter) consists of particles smaller than 2.5 micrometers — about 30 times thinner than a human hair. These particles can penetrate deep into the lungs and enter the bloodstream.

Health effects of PM2.5 exposure:

• Short-term: coughing, shortness of breath, aggravated asthma
• Long-term: reduced lung function, cardiovascular disease, premature death
• Most vulnerable: children, elderly, people with heart or lung disease

Common sources in urban areas: vehicle exhaust, construction dust, industrial emissions, wildfire smoke, residential wood burning.

Air Quality by ZIP Code in Mount Vernon

AQI varies across Mount Vernon's 2 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:

Wildfire Smoke Risk

Mount Vernon has an elevated wildfire smoke risk with an average smoke risk score of 20 (scale 0-100). There have been 58 fires recorded within 100 km of city ZIP codes.

Metric	Value
Avg. smoke risk score	20
Max smoke risk score	23
Fires within 100 km	58
High-risk ZIP codes	0

Wildfire smoke contains PM2.5, carbon monoxide, and volatile organic compounds. Even short-term exposure can trigger asthma attacks and respiratory distress.

Indoor Mold Risk

Mount Vernon has an average mold risk score of 50 out of 100, with 1 ZIP codes in the high-risk category.

Factor	Value
Mold risk score	50/100
Average humidity	71% RH
High-risk ZIPs	1
Peak season	winter high

Mold risk is influenced by humidity levels, housing age (older homes have more moisture issues), flood history, and water infrastructure quality. Indoor humidity above 60% creates favorable conditions for mold growth.

Signs of mold problems: musty odors, visible growth on walls or ceilings, worsening allergies indoors, condensation on windows. Professional mold testing ($300-$600) can identify hidden issues.

Health Recommendations

With good air quality (AQI 15), Mount Vernon residents can enjoy outdoor activities without significant restrictions. General tips:

• Monitor AQI during wildfire season for temporary spikes
• Use HEPA air purifiers indoors if you have respiratory conditions
• Maintain indoor humidity between 30-50% to prevent mold

Mount Vernon vs. Nearby Washington Cities

How Mount Vernon's air quality compares to nearby cities:

ZIP Codes in Mount Vernon

Mount Vernon covers 2 ZIP codes. Air quality can vary by neighborhood based on proximity to highways, industrial areas, and green spaces. Check your specific ZIP code for localized data.

Data Sources

• Air quality: EPA AirNow — real-time and historical AQI data
• Wildfire risk: FEMA National Risk Index
• Mold risk: Derived from EPA, FEMA, Census ACS (humidity, housing age, flood history)
• Monthly AQI: EPA Air Quality Statistics

Updated daily.