What Is the Air Quality in Kauai, Hawaii?
Kauai, Hawaii has an Air Quality Grade of A (excellent) with a 5-year median AQI of 15. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
Kauai, Hawaii Air Quality Snapshot
| Air Quality Grade | A82/100 |
| 5-Year Median AQI | 15 (Good) |
| Most Recent Median AQI (2022) | 13 (Good) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Improving (-0.72 AQI/yr) |
| Unhealthy Days (last 5 yr) | 0 |
| National Rank (cleanest = #1) | #34 of 1,020 (3th cleanest percentile) |
| Hawaii Rank | #1 of 4 |
What Does the A Grade Mean?
Kauai, Hawaii earns an A — it is among the cleanest U.S. cities tracked by EPA monitoring, with median AQI averaging just 15 over the past five years. Days in the "Good" category dominate the calendar; air-quality alerts are rare.
Kauai, Hawaii's 5-year median AQI of 15 is 26 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Hawaii, Kauai, Hawaii runs cleaner than the state average of 23 — a positive signal that local conditions (terrain, wind patterns, emission sources) are working in residents' favor.
For context within Hawaii: Hawaii, Hawaii currently holds the state's cleanest grade (A, AQI 25), while Honolulu, Hawaii sits at the bottom (B, AQI 29).
What's in Kauai, Hawaii's Air?
The dominant pollutant in Kauai, Hawaii is Fine Particulate Matter (PM2.5). Fine particulate matter — particles less than 2.5 micrometers across — comes mostly from combustion: vehicle exhaust, wildfire smoke, residential wood burning, and industrial emissions. Because these particles are small enough to enter the bloodstream, PM2.5 is the pollutant most strongly linked to cardiovascular disease, respiratory illness, and premature death.
Days by Dominant Pollutant (2022)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 76 | 84% |
| Nitrogen Dioxide | 14 | 16% |
Is the Air Getting Better or Worse?
Air quality in Kauai, Hawaii has been improving over the past decade, with median AQI dropping by roughly 0.7 points per year. That is consistent with the broader national pattern — most U.S. metros have seen steady reductions in particulate and ozone pollution since the 2010s as cleaner vehicles and power plants come online.
In 2014, Kauai, Hawaii posted a median AQI of 23. By 2022 that figure was 13 — a drop of 10 AQI points cleaner across 9 years of EPA records.
Year-by-Year AQI in Kauai, Hawaii
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 23 | 322 | 0 | PM2.5 |
| 2015 | 17 | 348 | 0 | PM2.5 |
| 2016 | 17 | 352 | 0 | PM2.5 |
| 2017 | 15 | 353 | 0 | PM2.5 |
| 2018 | 18 | 350 | 0 | PM2.5 |
| 2019 | 16 | 361 | 0 | PM2.5 |
| 2020 | 15 | 361 | 0 | PM2.5 |
| 2021 | 17 | 364 | 0 | PM2.5 |
| 2022 | 13 | 90 | 0 | PM2.5 |
Health Context for Kauai, Hawaii
Across the past five years, this area has logged just 0 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 0 days per year, or roughly one every other month. That is a low count by national standards.
For most healthy adults, current air quality in this area does not require any change in behavior. People with severe asthma, COPD, or recent cardiac events should still keep an eye on daily AQI alerts, especially during wildfire season. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
Kauai, Hawaii has an Air Quality Grade of A (excellent) with a 5-year median AQI of 15. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
The data source behind this answer is the EPA Air Quality System (AQS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
For readers turning this answer into action: cross-reference against the underlying the EPA Air Quality System (AQS) record before acting on time-sensitive decisions. The site renders the data as it was published; subsequent revisions can shift the picture, and the live federal data is always the authoritative current reference.
Source: EPA Outdoor Air Quality Data, 2026.