Bad Air Days in Kent County, Delaware: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 514 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (42% particle days).

Which months to watch

Most bad days here fall in June and May. 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 25 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 8 bad days on 348 monitored days.

Date	AQI	Main pollutant
2023-06-08	207	PM2.5
2023-06-07	199	PM2.5
2023-06-29	160	PM2.5
2016-05-25	136	Ozone
2018-07-10	133	Ozone

An ordinary day in Kent

Across 3,590 monitored days from 2016 to 2025, the air in Kent County rated Good on 73% of them, close to the 72% typical of monitored counties, and Moderate on 26%. The median day sat at AQI 42; one day in ten went above 60.

The pollutant setting the AQI on an ordinary day here:

ozone56%2,016 days
fine particles (PM2.5)44%1,574 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	276	85	4	0	41	122
2024	336	250	86	0	0	41	100
2023	348	216	124	8	3	46	207
2022	364	277	87	0	0	42	84
2021	360	260	98	2	0	42	108
2020	362	296	66	0	0	39	80
2019	365	248	117	0	0	44	85
2018	365	267	96	2	0	42	133
2017	361	264	96	1	0	42	101
2016	364	272	90	2	0	42	136
2015	365	245	120	0	0	44	100
2014	364	230	133	1	0	46	108
2013	357	221	136	0	0	46	100
2012	342	209	112	21	4	44	182
2011	365	270	90	5	2	41	172
2010	307	193	102	12	3	44	166

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

Nearby counties on file

New Castle County5/yr
Sussex County1/yr

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.