Bad Air Days in Hawaii County, Hawaii: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 522 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (100% particle days).

The bad-air season here

Most bad days here fall in June and May and March. Averaged over 2016 to 2025.

What actually helps here

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

The worst days on file

In 2000 to 2009 this county averaged 8 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2018, with 14 bad days on 365 monitored days.

Date	AQI	Main pollutant
2018-05-29	153	PM2.5
2018-06-04	151	PM2.5
2018-05-28	127	PM2.5
2018-06-16	124	PM2.5
2018-12-31	121	PM2.5

An ordinary day in Hawaii

Across 3,653 monitored days from 2016 to 2025, the air in Hawaii County rated Good on 71% of them, close to the 72% typical of monitored counties, and Moderate on 28%. The median day sat at AQI 36; one day in ten went above 55.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%3,653 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	314	51	0	0	32	93
2024	366	355	11	0	0	21	75
2023	365	336	29	0	0	23	71
2022	365	328	37	0	0	33	71
2021	365	336	29	0	0	27	65
2020	366	352	14	0	0	23	83
2019	365	357	8	0	0	21	81
2018	365	140	211	14	2	55	153
2017	365	82	283	0	0	58	98
2016	366	2	359	5	0	66	117
2015	365	12	353	0	0	63	99
2014	358	59	297	2	0	58	118
2013	365	14	351	0	0	61	94
2012	366	20	344	2	2	65	180
2011	365	83	282	0	0	58	85
2010	365	11	339	15	2	69	156

*2025 may be a partial year in EPA's file.

Nearby counties on file

Maui Countyunder 1/yr
Honolulu Countyunder 1/yr
Kauai County0/yr

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day.