Bad Air Days in Essex County, New Jersey: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 542 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (17% particle days).

When the bad days come in Essex

Most bad days here fall in July and May and June. 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.

The worst days on file

In 2000 to 2009 this county averaged 5 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2018, with 4 bad days on 364 monitored days.

Date	AQI	Main pollutant
2018-07-02	177	Ozone
2016-05-25	136	Ozone
2018-07-10	133	Ozone
2020-12-12	127	PM2.5
2021-07-20	125	PM2.5

Most days, not the worst ones

Across 2,460 monitored days from 2016 to 2022, the air in Essex County rated Good on 60% of them, less often than the 72% typical of monitored counties, and Moderate on 39%. The median day sat at AQI 45; one day in ten went above 64.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)61%1,489 days
ozone30%739 days
nitrogen dioxide9%227 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2022	269	177	92	0	0	44	97
2021	365	214	148	3	0	46	125
2020	366	226	139	1	0	44	127
2019	365	206	159	0	0	47	100
2018	364	219	141	4	1	43	177
2017	365	223	141	1	0	44	101
2016	366	217	146	3	0	46	136
2015	365	283	77	5	0	39	112
2014	365	258	102	5	0	43	116
2013	365	244	119	2	0	43	126
2012	366	190	163	13	0	50	140
2011	363	196	153	14	2	49	164
2010	365	226	122	17	3	45	164

New Jersey compared

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.