Lewis, Washington Air Quality
Lewis County, Washington (WA)
↓ Improvingover 10 years
10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days). This area has seen measurable air quality improvement over the decade.
Air Quality Day Breakdown
Number of days per year in each EPA AQI category. Green = Good (AQI 0-50), Yellow = Moderate (51-100), Orange = Unhealthy for Sensitive Groups (101-150), Red = Unhealthy or worse (151+).
Year-by-Year Data
| Year | Median AQI | 90th Pct | Max AQI | Good Days | Moderate | Unhealthy+ | Pollutant |
|---|---|---|---|---|---|---|---|
| 2023 | 25 | 54 | 159 | 314 | 46 | 2 | PM2.5 |
| 2022 | 26 | 66 | 198 | 285 | 70 | 10 | PM2.5 |
| 2021 | 23 | 46 | 71 | 328 | 22 | 0 | PM2.5 |
| 2020 | 25 | 46 | 258 | 314 | 20 | 1 | PM2.5 |
| 2019 | 27 | 54 | 66 | 308 | 57 | 0 | PM2.5 |
| 2018 | 28 | 58 | 172 | 298 | 61 | 6 | PM2.5 |
| 2017 | 26 | 57 | 162 | 302 | 60 | 3 | PM2.5 |
| 2016 | 26 | 44 | 70 | 340 | 26 | 0 | PM2.5 |
| 2015 | 30 | 53 | 154 | 311 | 49 | 1 | PM2.5 |
| 2014 | 31 | 54 | 78 | 312 | 53 | 0 | PM2.5 |
What This Means for Lewis County Residents
Lewis, Washington has received an Air Quality Grade of B (75/100) based on a decade of EPA monitoring data. The current median AQI of 25 falls in the "Good" range.
Encouragingly, air quality here has been improving, with the median AQI dropping by 6 points over the monitoring period. This trend suggests continued investment in emission controls and cleaner energy.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 3 unhealthy air quality days per year — days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity.