Best Cities for Air Quality in Hawaii
Ranking of cities with the cleanest air in Hawaii based on AQI data.
Cleanest air in Hawaii: Honolulu
Of the 1 Hawaii metro area EPA published a full year of AQI data for in 2025, Honolulu recorded the highest share of Good-air days: 355 of 365 monitored days (97.3%) at AQI 50 or below, with a median AQI of 29 and 0 days above AQI 100. Its peak reading that year was AQI 59. The pollutant that set the daily AQI most often was ground-level ozone (226 days).
| # | City (EPA area) | Good days (2025) | Median AQI | Days over 100 | Peak AQI | AQI now |
|---|---|---|---|---|---|---|
| 1 | HonoluluUrban Honolulu, HI | 355 / 365 (97.3%) | 29 | 0 | 59 | 28 |
Figures are EPA's published annual AQI summaries by metropolitan area (Annual AQI by CBSA, 2019–2025), retrieved 2026-09-07. The daily AQI EPA summarises is the highest value any monitor in the area reported that day, so these are metro-area readings, not statewide or rural ones.
Honolulu's air quality year by year
One clean year can be luck — a mild summer, no wildfire smoke. This is every year EPA has published for the Urban Honolulu, HI area, so you can see whether Honolulu's ranking is durable.
| Year | Days measured | Good days | Median AQI | Days over 100 | Days over 150 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|---|---|
| 2019 | 365 | 360 | 28 | 0 | 0 | 62 | ground-level ozone |
| 2020 | 366 | 363 | 28 | 0 | 0 | 63 | ground-level ozone |
| 2021 | 365 | 364 | 28 | 0 | 0 | 58 | ground-level ozone |
| 2022 | 365 | 356 | 29 | 0 | 0 | 57 | fine particulate matter (PM2.5) |
| 2023 | 365 | 337 | 31 | 1 | 0 | 117 | fine particulate matter (PM2.5) |
| 2024 | 366 | 360 | 31 | 0 | 0 | 85 | ground-level ozone |
| 2025 | 365 | 355 | 29 | 0 | 0 | 59 | ground-level ozone |
Across 2019–2025, Honolulu's air quality shows no clear trend: the area's median AQI held near 28 and days above AQI 100 stayed from about 0 to 0 per year (comparing the earlier and later halves of the period).
How Hawaii compares
Ranked by the median of its metro areas' median AQI in 2025, Hawaii is #2 cleanest of the 51 states EPA publishes metro AQI data for, at a median AQI of 29. The cleanest state on that measure is Alaska; the most polluted is Arizona. See the full state air quality rankings.
| Bordering state | Median metro AQI (2025) | National rank (cleanest first) |
|---|---|---|
| Oregon | 41 | #11 of 51 |
| Washington | 47 | #26 of 51 |
| California | 61 | #50 of 51 |
What this ranking does and does not cover
We track 1 Hawaii city. 1 has a full 2025 EPA record and is ranked above.
EPA's AQI is reported by metropolitan area, and the daily value is the worst reading from any monitor in that area. Rural Hawaii — and any town without a regulatory monitor — is not represented here. A high Good-day share means the monitored metro air was clean on most days; it is not a statement about a specific street, and it does not capture short pollution spikes between the daily summaries.