Bad Air Days in Lancaster County, Pennsylvania: 6 a Year
6 bad air days a year
More bad air days than three quarters of monitored counties. Ranked 167 of 996 monitored counties, where 1 is worst.
What makes them bad: mostly particles: smoke and dust (78% particle days).
When the bad days come in Lancaster
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Most bad days here fall in June and December and January and November. Averaged over 2016 to 2025.
What to buy, and what not to
- Particles (wildfire smoke, dust) cause enough bad days here to matter. A HEPA purifier sized to your bedroom removes them; run it with windows shut on bad days.
The worst days on file
In 2000 to 2009 this county averaged 28 bad days a year; in 2016 to 2025, 6. The air has improved. The worst recent year was 2023, with 14 bad days on 365 monitored days.
| Date | AQI | Main pollutant |
|---|---|---|
| 2023-06-07 | 321 | PM2.5 |
| 2023-06-08 | 292 | PM2.5 |
| 2023-06-29 | 177 | PM2.5 |
| 2023-06-06 | 169 | PM2.5 |
| 2023-06-30 | 162 | PM2.5 |
The air on a normal day
Across 3,653 monitored days from 2016 to 2025, the air in Lancaster County rated Good on 40% of them, less often than the 72% typical of monitored counties, and Moderate on 59%. The median day sat at AQI 53; one day in ten went above 75.
The pollutant setting the AQI on an ordinary day here:
- fine particles (PM2.5)75%2,741 days
- ozone25%909 days
Year by year
| Year | Days monitored | Good | Moderate | Over 100 | Over 150 | Median AQI | Highest AQI |
|---|---|---|---|---|---|---|---|
| 2025* | 365 | 221 | 142 | 2 | 0 | 45 | 119 |
| 2024 | 366 | 189 | 174 | 3 | 0 | 50 | 125 |
| 2023 | 365 | 108 | 243 | 14 | 5 | 58 | 321 |
| 2022 | 365 | 84 | 274 | 7 | 1 | 59 | 153 |
| 2021 | 365 | 100 | 257 | 8 | 1 | 56 | 156 |
| 2020 | 366 | 177 | 184 | 5 | 1 | 51 | 153 |
| 2019 | 365 | 160 | 195 | 10 | 1 | 52 | 159 |
| 2018 | 365 | 167 | 193 | 5 | 0 | 52 | 126 |
| 2017 | 365 | 122 | 239 | 4 | 0 | 55 | 128 |
| 2016 | 366 | 117 | 243 | 6 | 0 | 56 | 136 |
| 2015 | 365 | 121 | 234 | 10 | 0 | 56 | 140 |
| 2014 | 365 | 58 | 292 | 15 | 1 | 61 | 155 |
| 2013 | 365 | 152 | 205 | 8 | 0 | 54 | 142 |
| 2012 | 366 | 96 | 250 | 20 | 1 | 60 | 179 |
| 2011 | 365 | 93 | 252 | 20 | 3 | 60 | 161 |
| 2010 | 365 | 149 | 188 | 28 | 2 | 54 | 174 |
*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
- Berks County5/yr
- Delaware County4/yr
- Northampton County4/yr
- Montgomery 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.