Bad Air Days in Boone County, Kentucky: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 499 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 July and August and September. 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 Boone

In 2000 to 2009 this county averaged 17 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 7 bad days on 245 monitored days.

Date	AQI	Main pollutant
2023-08-21	156	Ozone
2018-07-13	151	Ozone
2023-06-02	133	Ozone
2023-06-28	133	Ozone
2024-08-27	129	Ozone

Most days, not the worst ones

Across 2,348 monitored days from 2016 to 2025, the air in Boone 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 39; one day in ten went above 54.

The pollutant setting the AQI on an ordinary day here:

ozone100%2,348 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	242	212	27	3	0	38	108
2024	230	183	46	1	0	43	129
2023	245	187	51	7	1	44	156
2022	199	173	26	0	0	41	97
2021	244	225	19	0	0	39	90
2020	242	218	24	0	0	36	87
2019	239	222	17	0	0	39	80
2018	243	218	23	2	1	38	151
2017	223	208	15	0	0	38	97
2016	241	212	29	0	0	38	87
2015	244	221	22	1	0	39	101
2014	245	231	14	0	0	37	80
2013	244	227	16	1	0	38	101
2012	245	179	59	7	0	43	150
2011	239	200	36	3	0	41	115
2010	245	193	50	2	0	42	136

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

Kentucky 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.