Bad Air Days in Dewey County, Oklahoma: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 500 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (25% particle days).

Which months to watch

Most bad days here fall in July and March and May and August. 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 Dewey

In 2000 to 2009 this county averaged 5 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2018, with 7 bad days on 362 monitored days.

Date	AQI	Main pollutant
2025-03-14	164	PM2.5
2017-03-07	134	PM2.5
2022-07-20	129	Ozone
2021-08-02	116	PM2.5
2018-08-03	115	Ozone

An ordinary day in Dewey

Across 3,617 monitored days from 2016 to 2025, the air in Dewey County rated Good on 66% of them, less often than the 72% typical of monitored counties, and Moderate on 33%. The median day sat at AQI 45; one day in ten went above 66.

The pollutant setting the AQI on an ordinary day here:

ozone55%2,002 days
fine particles (PM2.5)45%1,615 days

Dewey County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	364	232	131	1	1	46	164
2024	366	221	139	6	0	47	112
2023	365	221	144	0	0	46	100
2022	346	219	124	3	0	47	129
2021	365	261	103	1	0	44	116
2020	365	266	99	0	0	43	99
2019	365	230	135	0	0	44	93
2018	362	212	143	7	0	47	115
2017	358	262	94	2	0	43	134
2016	361	280	81	0	0	42	87
2015	348	256	92	0	0	42	96
2014	361	211	149	1	0	46	105
2013	365	202	160	3	0	48	112
2012	366	211	142	13	0	47	136
2011	362	187	159	16	0	50	143
2010	365	252	111	2	0	44	112

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

Nearby counties on file

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.