Bad Air Days in Polk County, Iowa: 2 a Year

2 bad air days a year

About the middle of monitored US counties. Ranked 449 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (54% particle days).

When the bad days come in Polk

Most bad days here fall in June and July 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 2 bad days a year; in 2016 to 2025, 2. Not much has changed. The worst recent year was 2023, with 15 bad days on 365 monitored days.

Date	AQI	Main pollutant
2020-07-04	199	PM2.5
2023-06-28	166	PM2.5
2023-07-16	159	PM2.5
2020-07-05	155	PM2.5
2023-06-27	154	PM2.5

The air on a normal day

Across 3,653 monitored days from 2016 to 2025, the air in Polk County rated Good on 64% of them, less often than the 72% typical of monitored counties, and Moderate on 35%. The median day sat at AQI 45; one day in ten went above 62.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)65%2,360 days
ozone35%1,261 days
nitrogen dioxide1%27 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	224	139	2	0	44	136
2024	366	247	119	0	0	45	93
2023	365	168	182	15	3	52	166
2022	365	273	92	0	0	41	89
2021	365	227	137	1	0	45	110
2020	366	261	103	2	2	42	199
2019	365	251	114	0	0	42	100
2018	365	225	138	2	0	46	112
2017	365	222	142	1	0	45	135
2016	366	244	121	1	0	44	138
2015	365	252	113	0	0	44	99
2014	365	227	138	0	0	44	93
2013	365	191	174	0	0	48	99
2012	366	169	197	0	0	52	100
2011	365	181	184	0	0	51	98
2010	365	180	182	3	0	51	116

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

Elsewhere in Iowa

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.