Bad Air Days in Montgomery County, Iowa: 1 a Year
1 bad air day a year
Fewer bad air days than most monitored US counties. Ranked 683 of 996 monitored counties, where 1 is worst.
What makes them bad: a mix of particles and ozone (50% particle days).
Which months to watch
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in June and August and September. Averaged over 2016 to 2025.
What to buy, and what not to
- 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 Montgomery
In 2000 to 2009 this county averaged 3 bad days a year; in 2016 to 2025, 1. The air has improved. The worst recent year was 2023, with 7 bad days on 364 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-09-06 | 147 | PM2.5 |
| 2025-08-01 | 133 | PM2.5 |
| 2016-05-07 | 121 | PM2.5 |
| 2023-06-03 | 115 | Ozone |
| 2023-06-14 | 115 | Ozone |
An ordinary day in Montgomery
Across 3,622 monitored days from 2016 to 2025, the air in Montgomery County rated Good on 70% of them, close to the 72% typical of monitored counties, and Moderate on 30%. The median day sat at AQI 43; one day in ten went above 59.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)64%2,325 days
- ozone36%1,297 days
Montgomery County by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 253 | 111 | 1 | 0 | 43 | 133 |
| 2024 | 354 | 272 | 82 | 0 | 0 | 42 | 80 |
| 2023 | 364 | 226 | 131 | 7 | 0 | 44 | 147 |
| 2022 | 363 | 305 | 58 | 0 | 0 | 39 | 79 |
| 2021 | 351 | 250 | 100 | 1 | 0 | 42 | 112 |
| 2020 | 366 | 277 | 89 | 0 | 0 | 41 | 79 |
| 2019 | 364 | 267 | 97 | 0 | 0 | 41 | 77 |
| 2018 | 365 | 219 | 146 | 0 | 0 | 46 | 93 |
| 2017 | 364 | 228 | 136 | 0 | 0 | 45 | 84 |
| 2016 | 366 | 232 | 133 | 1 | 0 | 44 | 121 |
| 2015 | 365 | 231 | 134 | 0 | 0 | 44 | 97 |
| 2014 | 364 | 196 | 167 | 1 | 0 | 48 | 107 |
| 2013 | 365 | 187 | 174 | 4 | 0 | 50 | 133 |
| 2012 | 365 | 183 | 177 | 5 | 0 | 50 | 112 |
| 2011 | 362 | 198 | 164 | 0 | 0 | 48 | 93 |
| 2010 | 309 | 164 | 143 | 2 | 0 | 49 | 112 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Webster County8/yr
- Scott County4/yr
- Palo Alto County4/yr
- Linn County3/yr
- Harrison County3/yr
- Clinton County3/yr
- Polk County2/yr
- Bremer County2/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.