Updated April 2026 · EPA AQS data
Compare Air Quality Between Any Two U.S. Cities
Side-by-side air quality across 1,020 U.S. cities — 10-year EPA Air Quality System data, with directly comparable Air Quality Grades (A–F), 5-year median AQI, dominant pollutants, and trend slopes. Pick any two cities and the tool builds the comparison.
Why City-to-City Comparison Beats National Averages
National AQI averages mask huge regional variation. The Pacific Northwest, the Mountain West, and the Northeast can each carry a "moderate" national reading while individual cities range from pristine to among the worst on the continent. A single national number can't tell you whether moving from Boise to Bend will improve your daily air quality — but a direct comparison can, because the underlying numbers are the same EPA monitor readings interpreted through the same Air Quality Grade formula.
The EPA AirNow service publishes today's AQI for individual cities, but it doesn't surface the multi-year context — whether the air you breathe today is normal for that city, getting better, or unusual. The comparison tool here pairs a 10-year backdrop with a side-by-side view so you can see both today's numbers and the trajectory.
The biggest pairwise differences in the dataset tend to fall into a few buckets: (a) high-elevation rural towns vs. dense urban metros (population density alone drives a 20–40 AQI gap on average), (b) Western cities affected by wildfire smoke vs. those upwind of fire-prone regions (year-over-year volatility is the discriminator), and (c) Northeast cities pre- and post-coal-plant retirement (the median has fallen 10–15 points in many cases over the decade tracked).
Compare Air Quality
Compare air quality trends, grades, and pollutants between any two US cities.
Frequently Asked Questions
How does this comparison tool work?
Pick any two of 1,020 U.S. cities tracked here and the tool pulls 10 years of EPA Air Quality System data side-by-side: 5-year median AQI, 10-year trend slope, dominant pollutant, and the count of "Unhealthy for Sensitive Groups" days. Each city's Air Quality Grade (A–F) is computed from the same four-factor weighted formula, so the letter grades are directly comparable.
Which numbers actually matter when comparing two cities?
For long-term health, the 5-year median AQI is the most important number — it reflects what residents breathe most days, averaged across noise. The 10-year trend tells you whether that picture is improving or deteriorating. The dominant pollutant matters because the same AQI can come from different causes (PM2.5 from wildfires looks identical to PM2.5 from traffic on a daily reading, but has different mitigation implications). Day counts in the unhealthy categories matter for people with asthma, COPD, or heart disease.
Why might two cities with the same AQI feel very different?
Two cities can post identical median AQI numbers and have very different lived experiences. A coastal city with intermittent ozone spikes feels stable most days but sees occasional acute alerts; a Western city with rising wildfire smoke feels clean for months at a time then unbreathable for weeks. The trend column captures this — a worsening city with the same median AQI as a stable city carries higher future risk.
Are the comparisons fair across regions?
Yes. Every city in the dataset is graded on the same four-factor formula using the same EPA AQS Annual AQI by County data. The composite score is independent of region, climate, or population, so comparing a Pacific Northwest city to a Gulf Coast city or a Mountain West town to a Northeast metro is methodologically apples-to-apples. The pollutant breakdown adds context where regional differences are dominant (e.g., ozone-heavy Southwest vs. PM-heavy Pacific NW).
Can I save or share a comparison?
Each comparison is reflected in the URL — copy and paste the link to share. The underlying city profiles are deep-linked from the comparison view so you can drill into the year-by-year detail behind any number you see.
How the Comparison Numbers Are Calculated
For each city in the dataset, the 5-year median AQI summarizes the most recent five complete years of EPA AQS Annual AQI by County data. The 10-year trend slope is from a linear regression on annual median AQI values across the past decade. The composite Air Quality Grade weights median AQI at 40%, trend at 30%, unhealthy-day count at 20%, and dominant pollutant type at 10%. Both cities in any given comparison run through the identical formula. Read the full methodology.
Source: U.S. EPA Air Quality System (AQS), Annual AQI by County 2014–present. Public domain.
Last updated 2026-04-06 · 1,020 U.S. cities tracked.