States: Unhealthy Air Days
EPA monitor data through 2025 · Updated August 13, 2026
Every U.S. state and territory with air monitoring, ranked by days above an Air Quality Index of 100. California recorded the most in 2025, at 195 days.
A statewide figure is the worst monitor anywhere in the state on each day. It answers “was the air unhealthy somewhere?” rather than “what did a typical resident breathe?”, so large states with many monitors read high. EPA reports the AQI for metropolitan areas rather than states for that reason — see the metro rankings.
| State | Unhealthy days | Pre-2013 rules | Good days | Main driver | Year |
|---|---|---|---|---|---|
| California | 195 | 147 | 1 | ozone | 2025 |
| Texas | 135 | 106 | 3 | ozone | 2025 |
| New Mexico | 84 | 63 | 35 | ozone | 2025 |
| Arizona | 69 | 46 | 11 | ozone | 2025 |
| Michigan | 37 | 21 | 93 | fine particles | 2025 |
| Colorado | 32 | 11 | 53 | ozone | 2025 |
| Wisconsin | 32 | 23 | 176 | ozone and fine particles equally | 2025 |
| Illinois | 30 | 18 | 98 | ozone | 2025 |
| New York | 30 | 18 | 133 | ozone | 2025 |
| Ohio | 30 | 16 | 55 | ozone | 2025 |
| Wyoming | 30 | 28 | 98 | fine particles | 2025 |
| Indiana | 29 | 20 | 67 | ozone | 2025 |
| Minnesota | 29 | 22 | 161 | fine particles | 2025 |
| Nevada | 29 | 17 | 70 | ozone | 2025 |
| Washington | 25 | 22 | 96 | fine particles | 2025 |
| Connecticut | 24 | 18 | 214 | ozone | 2025 |
| Oregon | 23 | 18 | 114 | fine particles | 2025 |
| Alaska | 22 | 19 | 163 | fine particles | 2025 |
| Oklahoma | 21 | 9 | 92 | ozone | 2025 |
| Pennsylvania | 21 | 10 | 90 | fine particles | 2025 |
| Missouri | 19 | 15 | 79 | ozone | 2025 |
| New Jersey | 19 | 10 | 171 | ozone | 2025 |
| North Dakota | 19 | 16 | 221 | fine particles | 2025 |
| Utah | 19 | 6 | 82 | ozone | 2025 |
| Georgia | 18 | 10 | 59 | fine particles | 2025 |
| Maine | 17 | 11 | 224 | fine particles | 2025 |
| Iowa | 16 | 10 | 109 | fine particles | 2025 |
| Idaho | 15 | 11 | 71 | fine particles | 2025 |
| Florida | 13 | 8 | 39 | fine particles | 2025 |
| Kentucky | 13 | 7 | 141 | ozone | 2025 |
| Montana | 12 | 9 | 108 | fine particles | 2025 |
| Kansas | 10 | 4 | 119 | ozone | 2025 |
| Massachusetts | 10 | 6 | 228 | ozone | 2025 |
| South Dakota | 10 | 6 | 123 | fine particles | 2025 |
| Tennessee | 10 | 7 | 118 | ozone | 2025 |
| Louisiana | 9 | 1 | 68 | ozone | 2025 |
| New Hampshire | 8 | 3 | 239 | ozone | 2025 |
| Delaware | 7 | 3 | 223 | ozone | 2025 |
| Arkansas | 6 | 2 | 97 | ozone | 2025 |
| Maryland | 6 | 3 | 193 | ozone | 2025 |
| Nebraska | 6 | 1 | 176 | ozone | 2025 |
| South Carolina | 5 | 2 | 105 | fine particles | 2025 |
| Vermont | 5 | 3 | 267 | fine particles | 2025 |
| Virginia | 5 | 3 | 188 | ozone | 2025 |
| District Of Columbia | 4 | 3 | 241 | ozone and fine particles equally | 2025 |
| Puerto Rico | 4 | 1 | 214 | ozone and fine particles equally | 2025 |
| Rhode Island | 4 | 2 | 258 | ozone | 2025 |
| Alabama | 3 | 2 | 96 | fine particles | 2025 |
| North Carolina | 3 | 2 | 96 | fine particles | 2025 |
| Mississippi | 1 | 1 | 99 | ozone | 2025 |
| West Virginia | 1 | 0 | 185 | ozone | 2025 |
| Hawaii | 0 | 0 | 310 | ozone and fine particles equally | 2025 |
Latest year with monitoring data for each state. “Unhealthy days” means the Air Quality Index exceeded 100, the level at which EPA begins warning sensitive groups. The pre-2013 column applies the AQI rules in force before EPA's 2013 and 2015 revisions to the same monitor data, for comparison with older reports — why that matters.
Sources
- EPA AirData daily monitor files. Methods and validation.
- Download the full dataset.