Bad Air Days in Lehigh County, Pennsylvania: 2 a Year
2 bad air days a year
About the middle of monitored US counties. Ranked 458 of 996 monitored counties, where 1 is worst.
What makes them bad: a mix of particles and ozone (48% particle days).
The bad-air season here
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in June and July and February. 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 worst days on file
In 2000 to 2009 this county averaged 24 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 7 bad days on 363 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-06-07 | 337 | PM2.5 |
| 2023-06-08 | 193 | PM2.5 |
| 2023-06-06 | 169 | PM2.5 |
| 2023-06-29 | 167 | PM2.5 |
| 2023-06-30 | 164 | PM2.5 |
The air on a normal day
Across 3,604 monitored days from 2016 to 2025, the air in Lehigh County rated Good on 65% of them, less often than the 72% typical of monitored counties, and Moderate on 35%. The median day sat at AQI 44; one day in ten went above 64.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)56%2,008 days
- ozone43%1,556 days
- coarse dust (PM10)1%40 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 361 | 260 | 100 | 1 | 0 | 41 | 115 |
| 2024 | 353 | 267 | 84 | 2 | 0 | 39 | 119 |
| 2023 | 363 | 230 | 126 | 7 | 5 | 43 | 337 |
| 2022 | 359 | 246 | 113 | 0 | 0 | 42 | 99 |
| 2021 | 353 | 198 | 154 | 1 | 1 | 47 | 154 |
| 2020 | 359 | 262 | 97 | 0 | 0 | 41 | 93 |
| 2019 | 360 | 254 | 103 | 3 | 0 | 43 | 119 |
| 2018 | 365 | 221 | 142 | 2 | 0 | 43 | 126 |
| 2017 | 365 | 241 | 123 | 1 | 0 | 44 | 115 |
| 2016 | 366 | 156 | 204 | 6 | 0 | 52 | 129 |
| 2015 | 365 | 319 | 43 | 3 | 0 | 34 | 108 |
| 2014 | 365 | 334 | 30 | 1 | 0 | 35 | 112 |
| 2013 | 365 | 317 | 46 | 2 | 0 | 35 | 101 |
| 2012 | 362 | 308 | 44 | 10 | 1 | 34 | 151 |
| 2011 | 351 | 302 | 40 | 9 | 0 | 32 | 147 |
| 2010 | 363 | 278 | 65 | 20 | 2 | 31 | 172 |
*2025 may be a partial year in EPA's file.
Nearby counties on file
- Allegheny County12/yr
- Philadelphia County9/yr
- Bucks County8/yr
- Warren Countythin data
- Lancaster County6/yr
- Berks County5/yr
- Delaware County4/yr
- Northampton County4/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.