Bad Air Days in Hunterdon County, New Jersey: 3 a Year

3 bad air days a year

About the middle of monitored US counties. Ranked 377 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (13% particle days).

When the bad days come in Hunterdon

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

What to buy, and what not to

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.

Better or worse than it was

In 2000 to 2009 this county averaged 26 bad days a year; in 2016 to 2025, 3. The air has improved. The worst recent year was 2023, with 10 bad days on 364 monitored days.

Date	AQI	Main pollutant
2023-06-07	262	PM2.5
2023-06-08	188	PM2.5
2018-07-02	179	Ozone
2023-06-30	172	Ozone
2016-05-26	156	Ozone

The air on a normal day

Across 3,615 monitored days from 2016 to 2025, the air in Hunterdon County rated Good on 69% of them, close to the 72% typical of monitored counties, and Moderate on 30%. The median day sat at AQI 42; one day in ten went above 62.

The pollutant setting the AQI on an ordinary day here:

ozone50%1,821 days
fine particles (PM2.5)50%1,794 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	361	268	90	3	0	41	122
2024	365	266	99	0	0	41	100
2023	364	233	121	10	4	44	262
2022	364	263	101	0	0	42	93
2021	364	249	115	0	0	43	97
2020	364	265	99	0	0	41	87
2019	362	256	105	1	0	43	108
2018	352	236	111	5	2	43	179
2017	364	237	123	4	0	44	122
2016	355	234	114	7	1	43	156
2015	363	280	79	4	0	39	115
2014	363	245	116	2	0	42	105
2013	365	246	115	4	0	42	119
2012	363	203	150	10	0	48	143
2011	362	200	147	15	2	48	156
2010	364	199	141	24	2	47	169

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

Elsewhere in New Jersey

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, and on why a purifier does not touch ozone in smoke vs ozone.