Air Quality by State

Coverage spans all 50 U.S. states and DC, average air quality metrics across all 53 jurisdictions, based on EPA Air Quality System (AQS) county-level monitoring data for 2020-2025. Data from the EPA Air Quality System (AQS) and AirNow, covering all 50 states; see our methodology.

Hawaii leads state Good-day share; Arizona has the lowest among 53 monitored jurisdictions

According to the U.S. EPA Air Quality System, this directory ranks 53 jurisdictions on county-derived annual AQI and Good-day share. Use it to compare state patterns, then open a state page for county detail. These are historical annual records, not live conditions or health guidance.

Data source EPA Air Quality System (AQS)

Hawaii Good share
Hawaii Good share: 93.8%
Arizona Good share
Arizona Good share: 60.7%
Jurisdictions
Jurisdictions: 53
With monitors
With monitors: 53

from the compiled EPA AQS release in this database.

Find and sort states

State directory

National air-quality trend strip across 53 states Sparkline-style distribution of average good-pct across all states, sorted high to low. National good-day distribution 53 states · sorted high → low % good days
53 U.S. states monitoring station coverage Grid of states for 53 U.S. states, color-encoded by good-air-quality share, with antenna icons marking jurisdictions hosting active EPA AQS monitoring stations. Monitoring coverage 53 of 53 states · 100.0% covered Tile color = good-day share 90%+ 75%+ 50%+ 25%+ <25% 53 U.S. states · states shown: 48 of 53
53 actively-monitored states · 100.0% covered (53 U.S. states)

State comparison table

Showing 53 of 53 jurisdictions .

State Counties Good Days % Typical County AQI
Hawaii 3 93.8% 27
Virgin Islands 1 89.3% 21
Maine 11 87.0% 35
Virginia 30 86.5% 34
Montana 23 85.9% 25
Wyoming 17 85.1% 31
Nebraska 11 85.0% 32
New Hampshire 7 84.9% 37
Alaska 8 84.4% 20
Puerto Rico 8 84.0% 22
Vermont 4 83.8% 32
Massachusetts 13 83.1% 38
Rhode Island 3 83.0% 36
Washington 31 82.2% 30
Maryland 16 81.8% 40
New York 27 81.3% 37
North Carolina 34 81.0% 39
South Dakota 10 80.8% 35
Kentucky 25 80.6% 39
Tennessee 23 80.3% 38
North Dakota 9 79.4% 38
Idaho 19 78.2% 33
West Virginia 13 78.2% 39
Florida 38 77.4% 41
Oregon 21 76.9% 32
Minnesota 23 76.8% 35
Connecticut 8 76.7% 40
Nevada 9 76.5% 41
Wisconsin 29 76.5% 38
Missouri 21 75.9% 40
New Jersey 15 75.5% 40
Kansas 12 74.7% 39
Michigan 27 74.7% 38
Louisiana 22 74.6% 41
Delaware 3 74.1% 41
Alabama 15 73.9% 40
Pennsylvania 38 73.8% 40
Mississippi 10 72.9% 42
Indiana 33 71.8% 41
Colorado 30 71.7% 40
South Carolina 13 71.3% 43
Arkansas 11 71.2% 45
Illinois 23 70.0% 42
New Mexico 16 69.1% 39
Oklahoma 20 68.1% 43
Ohio 37 67.0% 43
Iowa 15 66.8% 42
District of Columbia 1 66.0% 45
Texas 45 65.6% 42
Utah 17 65.4% 42
Georgia 26 65.0% 43
California 47 61.2% 46
Arizona 13 60.7% 45

Explore well-covered counties by state

Continue from the state comparison into county records with at least 100 monitored days. These links favor the four most complete annual records available in each state, rather than thin samples.