Bad Air Days in Jefferson County, Ohio: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 578 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (73% particle days).

The bad-air season here

Most bad days here fall in June and July and February. 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 25 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 4 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-28	229	PM2.5
2023-06-29	217	PM2.5
2021-07-20	157	PM2.5
2019-02-03	123	PM2.5
2021-07-19	123	PM2.5

The air on a normal day

Across 3,605 monitored days from 2016 to 2025, the air in Jefferson County rated Good on 44% of them, less often than the 72% typical of monitored counties, and Moderate on 56%. The median day sat at AQI 51; one day in ten went above 68.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)77%2,776 days
ozone23%828 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	195	169	1	0	49	101
2024	366	227	139	0	0	45	93
2023	365	188	173	4	2	49	229
2022	365	149	216	0	0	53	97
2021	358	123	232	3	1	55	157
2020	359	263	95	1	0	42	112
2019	364	143	219	2	0	53	123
2018	344	96	246	2	0	55	108
2017	359	96	263	0	0	56	99
2016	360	105	253	2	0	56	105
2015	354	98	252	4	0	58	117
2014	361	98	258	5	0	57	150
2013	360	158	198	4	0	53	147
2012	366	104	246	16	0	58	140
2011	362	118	238	6	0	57	115
2010	365	121	237	7	1	57	152

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

Ohio 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.