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

2 bad air days a year

About the middle of monitored US counties. Ranked 468 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (9% particle days).

Which months to watch

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

In 2000 to 2009 this county averaged 23 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 6 bad days on 363 monitored days.

Date	AQI	Main pollutant
2023-06-30	154	Ozone
2016-05-26	151	Ozone
2023-06-29	151	PM2.5
2023-06-08	148	PM2.5
2016-05-25	143	Ozone

Most days, not the worst ones

Across 3,600 monitored days from 2016 to 2025, the air in Morris County rated Good on 88% of them, more often than the 72% typical of monitored counties, and Moderate on 12%. The median day sat at AQI 36; one day in ten went above 54.

The pollutant setting the AQI on an ordinary day here:

ozone87%3,123 days
fine particles (PM2.5)11%381 days
nitrogen dioxide3%96 days

Morris County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	326	275	48	3	0	39	129
2024	366	305	59	2	0	37	108
2023	363	314	43	6	2	37	154
2022	360	320	40	0	0	36	84
2021	363	327	36	0	0	36	97
2020	366	341	25	0	0	35	84
2019	364	325	39	0	0	36	87
2018	365	319	41	5	0	35	136
2017	363	318	42	3	0	35	115
2016	364	312	49	3	1	35	151
2015	365	304	58	3	0	37	108
2014	360	270	89	1	0	40	112
2013	361	284	71	6	0	39	122
2012	359	272	77	10	1	37	156
2011	365	283	72	10	0	38	147
2010	365	260	96	9	2	39	172

*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.