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

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 533 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (0% particle days).

Which months to watch

Most bad days here fall in June and September. 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 23 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2016, with 3 bad days on 213 monitored days.

Date	AQI	Main pollutant
2018-07-14	140	Ozone
2022-06-21	122	Ozone
2022-06-22	115	Ozone
2023-06-02	112	Ozone
2023-06-10	105	Ozone

An ordinary day in Miami

Across 2,392 monitored days from 2016 to 2025, the air in Miami County rated Good on 86% of them, more often than the 72% typical of monitored counties, and Moderate on 14%. The median day sat at AQI 41; one day in ten went above 58.

The pollutant setting the AQI on an ordinary day here:

ozone100%2,392 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	240	202	37	1	0	40	101
2024	245	198	46	1	0	43	101
2023	244	193	48	3	0	43	112
2022	245	214	29	2	0	39	122
2021	245	215	30	0	0	40	87
2020	229	217	12	0	0	39	93
2019	241	226	15	0	0	40	77
2018	245	207	37	1	0	40	140
2017	245	210	34	1	0	40	101
2016	213	164	46	3	0	43	101
2015	213	177	34	2	0	42	105
2014	214	181	32	1	0	41	105
2013	214	175	37	2	0	42	105
2012	213	131	68	14	1	47	177
2011	214	145	62	7	0	45	126
2010	213	146	65	2	0	44	133

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

Elsewhere in Ohio

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.