Bad Air Days in Jefferson Parish, Louisiana: 1 a Year

1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 641 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 Jefferson

Most bad days here fall in May and January and August and September. Averaged over 2016 to 2025.

Is a purifier worth it 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.

Better or worse than it was

In 2000 to 2009 this county averaged 19 bad days a year; in 2016 to 2025, 1. The air has improved. The worst recent year was 2023, with 4 bad days on 364 monitored days.

Date	AQI	Main pollutant
2024-01-01	188	PM2.5
2016-07-02	126	Ozone
2017-05-09	126	Ozone
2023-01-01	126	PM2.5
2017-09-14	122	Ozone

Most days, not the worst ones

Across 3,639 monitored days from 2016 to 2025, the air in Jefferson Parish rated Good on 67% of them, less often than the 72% typical of monitored counties, and Moderate on 33%. The median day sat at AQI 44; one day in ten went above 61.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)56%2,035 days
ozone43%1,578 days
nitrogen dioxide1%26 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	227	137	1	0	47	101
2024	366	224	141	1	1	46	188
2023	364	181	179	4	0	51	126
2022	362	219	143	0	0	46	96
2021	355	277	76	2	0	40	105
2020	366	280	86	0	0	40	87
2019	365	269	96	0	0	42	84
2018	365	207	157	1	0	47	101
2017	365	249	114	2	0	43	126
2016	366	290	75	1	0	42	126
2015	365	226	139	0	0	44	100
2014	365	206	154	5	0	48	122
2013	363	256	105	2	0	44	115
2012	360	205	150	5	0	48	129
2011	365	159	198	8	0	52	143
2010	365	137	217	11	1	53	169

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

Elsewhere in Louisiana

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.