States with the Cleanest Air, Hawaii Leads (2026)

1. EPA annual air quality by county, 2025 · 2025, with 2024 where 2025 is not yet filed
2. EPA annual air quality by county, 2024
3. EPA annual fine particle readings by monitor, 2025

How we got this. The Clean Air Score is The Honest Local’s own recipe. Each source ranks every place on its own from 0 to 100 and the score is the average, so a place has to do well on all of them to lead. We don't grade air on one count alone, so we blend two EPA readings. The share of monitored days in the year the EPA rated Good, and the average fine particle concentration the EPA's own monitors measured that year, a longer look at what hangs in the air than any one day's category. Each source ranks every place against every other place that has it and the average of the two ranks is the score that decides the list. The plain share of Good days is still what we show you. A city uses its own county. For a state we never hand you one county's reading and call it the state's. We weight every county in the state by population, for each source on its own. Connecticut is a real gap. The federal tables no longer agree on what a Connecticut county is, so there's no population to weight by and we use a plain average of the counties the EPA covers, noted in that row. It refreshes once a year, when the EPA publishes the prior year. For Hawaii, that means population-weighted mean of % across 3 EPA-covered counties in Hawaii (of the state's total counties; many rural counties have no monitor).

Rankings by The Honest Local from public data, one page per list, refreshed on each source’s own cycle. Places with no reading are left out rather than estimated. Every value on this page carries its source in the page’s structured data.