Bad Air Days in Custer County, Idaho

Not enough data

EPA monitors in Custer County ran on too few days between 2016 and 2025 to give a fair yearly count (about 29% of days covered). Neighbouring counties below are a better guide.

Is a purifier worth it here?

EPA monitors here ran too few days to give a fair yearly count. Use AirNow for today's air.

Better or worse than it was

The worst recent year was 2024, with 6 bad days on 109 monitored days.

Date	AQI	Main pollutant
2016-08-01	170	PM2.5
2024-09-06	152	PM2.5
2017-09-07	142	PM2.5
2024-08-07	138	PM2.5
2016-08-22	135	PM2.5

An ordinary day in Custer

Across 1,052 monitored days from 2016 to 2025, the air in Custer County rated Good on 92% of them, more often than the 72% typical of monitored counties, and Moderate on 6%. The median day sat at AQI 8; one day in ten went above 42.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%1,052 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	96	93	3	0	0	10	56
2024	109	94	9	6	1	6	152
2023	104	103	1	0	0	8	60
2022	105	98	7	0	0	7	98
2021	110	93	17	0	0	8	99
2020	115	105	7	3	0	7	126
2019	96	95	1	0	0	8	51
2018	90	85	3	2	0	7	128
2017	111	100	8	3	0	7	142
2016	116	103	9	4	1	11	170
2015	117	113	4	0	0	8	93
2014	110	107	3	0	0	9	54
2013	100	91	7	2	0	9	110
2012	109	90	15	4	2	12	170
2011	102	100	2	0	0	9	78
2010	110	110	0	0	0	10	47

*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.