Bad Air Days in Union County, New Jersey: under 1 a Year

under 1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 715 of 996 monitored counties, where 1 is worst.

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

Which months to watch

Most bad days here fall in June and July and December. 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 14 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2023, with 5 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-07	227	PM2.5
2023-06-08	179	PM2.5
2023-06-30	158	PM2.5
2023-06-06	157	PM2.5
2021-07-20	139	PM2.5

Most days, not the worst ones

Across 3,651 monitored days from 2016 to 2025, the air in Union County rated Good on 49% of them, less often than the 72% typical of monitored counties, and Moderate on 51%. The median day sat at AQI 50; one day in ten went above 64.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)89%3,246 days
nitrogen dioxide11%402 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	363	222	140	1	0	44	111
2024	366	229	137	0	0	43	85
2023	365	163	197	5	4	52	227
2022	365	191	174	0	0	49	82
2021	365	157	207	1	0	52	139
2020	366	198	167	1	0	48	111
2019	365	167	198	0	0	52	100
2018	365	156	209	0	0	52	96
2017	365	144	220	1	0	53	101
2016	366	152	214	0	0	52	90
2015	365	146	217	2	0	53	107
2014	365	141	220	4	0	54	141
2013	365	153	211	1	0	52	107
2012	364	156	208	0	0	53	96
2011	364	107	250	7	0	56	118
2010	365	147	214	4	0	54	108

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

Nearby counties on file

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.