Kauai County, Hawaii air quality history

Daily Air Quality Index summaries from EPA monitors in Kauai, Hawaii, 1985–2022.

100%

Good days in 2021

Median daily AQI, 2021

Days above 100 in 2021

364

Days with an AQI in 2021 (of 365)

In 2021, EPA reported a daily Air Quality Index (AQI) for Kauai, Hawaii on 364 days. 364 of those days (100%) were in the Good range, and the median daily AQI was 17. That median is lower than the typical monitored county in Hawaii (median 24 across 4 counties), and lower than the typical monitored U.S. county (41). The main pollutant was fine particles (PM2.5) on 329 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 98% in 2005–2011 versus 99% in 2019–2021.

The most recent year with data for this county is 2022; EPA's files for 2023–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1999, 2000, 2002, 2003, 2004, 2022…) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2021

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Fine particles (PM2.5)	329	90%
Nitrogen dioxide (NO₂)	35	10%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Median AQI	90th pct.	Max AQI	Main pollutant
2022	90	90	0	13	26	38	PM2.5
2021	364	364	0	17	29	47	PM2.5
2020	365	361	4	15	32	52	PM2.5
2019	363	361	2	16	31	70	PM2.5
2018	355	350	5	18	34	56	PM2.5
2017	359	353	6	15	35	59	PM2.5
2016	358	352	6	17	36	59	PM2.5
2015	362	348	14	17	41	59	PM2.5
2014	341	322	19	23	42	61	PM2.5
2013	365	351	14	19	42	58	PM2.5
2012	365	293	72	36	54	64	PM2.5
2011	274	255	19	23	47	64	PM2.5
2006	335	335	0	10	19	31	PM10
2005	220	220	0	13	22	28	PM10
2004	52	52	0	14	19	26	PM10
2003	61	61	0	14	22	29	PM10
2002	42	42	0	12	16	25	PM10
2000	24	24	0	15	25	36	PM10
1999	54	54	0	16	23	32	PM10
1998	46	46	0	18	28	29	PM10
1997	50	50	0	14	21	29	PM10
1996	57	57	0	17	27	38	PM10
1995	57	57	0	15	23	34	PM10
1994	45	45	0	19	24	30	PM10
1993	42	42	0	13	20	38	PM10
1992	40	40	0	16	22	30	PM10
1991	48	48	0	15	22	38	PM10
1990	35	35	0	15	24	29	PM10
1989	47	47	0	15	26	31	PM10
1988	47	47	0	16	20	28	PM10
1987	53	53	0	18	23	35	PM10
1986	52	52	0	19	31	39	PM10
1985	13	13	0	17	29	44	PM10

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

All monitored counties in Hawaii

Source: U.S. EPA AirData, “Annual AQI by County” files for 1985–2022 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem