Bad Air Days in Honolulu County, Hawaii: under 1 a Year

under 1 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 951 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 January. 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 record for Honolulu

In 2000 to 2009 this county averaged 1 bad days a year; in 2016 to 2025, under 1. Not much has changed. The worst recent year was 2023, with 1 bad day on 365 monitored days.

Date	AQI	Main pollutant
2023-01-01	117	PM2.5
2024-01-01	85	PM2.5
2018-01-01	73	PM2.5
2023-08-08	73	PM2.5
2017-03-13	68	PM2.5

The air on a normal day

Across 3,653 monitored days from 2016 to 2025, the air in Honolulu County rated Good on 96% of them, more often than the 72% typical of monitored counties, and Moderate on 4%. The median day sat at AQI 30; one day in ten went above 42.

The pollutant setting the AQI on an ordinary day here:

ozone60%2,186 days
fine particles (PM2.5)39%1,412 days
coarse dust (PM10)1%34 days

Honolulu County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	355	10	0	0	29	59
2024	366	360	6	0	0	31	85
2023	365	337	27	1	0	31	117
2022	365	356	9	0	0	29	57
2021	365	364	1	0	0	28	58
2020	366	363	3	0	0	28	63
2019	365	360	5	0	0	28	62
2018	365	353	12	0	0	31	73
2017	365	340	25	0	0	32	68
2016	366	330	36	0	0	32	64
2015	365	283	82	0	0	39	66
2014	359	325	33	1	1	32	195
2013	365	294	71	0	0	37	71
2012	366	260	106	0	0	41	78
2011	365	206	158	1	0	43	101
2010	365	190	174	1	1	49	155

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

Elsewhere in Hawaii

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.