Jefferson, Washington Air Quality
Jefferson County, Washington (WA)
↓ Improvingover 10 years
How Jefferson, Washington Air Quality Compares
Jefferson, Washington's median AQI of 21is 49% better than the national average of 41. Air quality has improved by 6 AQI points over the past decade. The area averages 2 unhealthy air days per year. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
Jefferson, Washington Air Quality: The Full Picture
Jefferson, Washington (Jefferson County) holds an AirHistory Air Quality Grade of B (good, scoring 77 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 6 points between 2014 (27) and 2023 (21), and the five-year median now sits at 22 — inside the "Good" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Fine Particulate Matter (PM2.5). In 2023, it set the daily AQI on 350 of 350 monitored days (100% of the year), making it the controlling pollutant for the B grade. The single worst reading logged that year hit an AQI of 88 (Moderate), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 39.
In 2023, Jefferson County recorded 336 "Good" air days (96% of the 350 days with valid AQI data), 14 "Moderate" days, and 0 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 8 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 2 per year.
The decade-long trend is improving: median AQI has been dropping by roughly 0.67 points per year. The cleanest year in the record was 2021 (median AQI 20), and the most polluted was 2014 (median AQI 27). Because the data come straight from federally certified EPA monitors, these figures track the Washington county the monitors physically sit in rather than a city boundary.
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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 | 21 | 39 | 88 | 336 | 14 | 0 | PM2.5 |
| 2022 | 21 | 41 | 90 | 327 | 22 | 0 | PM2.5 |
| 2021 | 20 | 32 | 79 | 352 | 6 | 0 | PM2.5 |
| 2020 | 23 | 43 | 232 | 321 | 11 | 8 | PM2.5 |
| 2019 | 26 | 42 | 57 | 344 | 21 | 0 | PM2.5 |
| 2018 | 25 | 48 | 184 | 327 | 26 | 6 | PM2.5 |
| 2017 | 24 | 51 | 108 | 328 | 36 | 1 | PM2.5 |
| 2016 | 24 | 39 | 65 | 336 | 12 | 0 | PM2.5 |
| 2015 | 26 | 51 | 75 | 275 | 32 | 0 | PM2.5 |
| 2014 | 27 | 52 | 68 | 302 | 40 | 0 | PM2.5 |
What This Means for Jefferson County Residents
Jefferson, Washington has received an Air Quality Grade of B (77/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 21 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 2 unhealthy air quality days per year, days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity. The American Lung Association's State of the Air report provides additional context on long-term health risks from air pollution exposure.
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Frequently Asked Questions
Jefferson, Washington has a current median AQI of 21, which falls in the "Good" range. The area has received an Air Quality Grade of B (77/100) based on 10 years of EPA monitoring data.
Air quality in Jefferson, Washington is improving over the past decade. The median AQI has changed by -6 points from 2014 to 2023.
Jefferson, Washington averages 2 unhealthy air quality days per year over the past 5 years. On these days, sensitive groups including children, the elderly, and those with respiratory conditions should limit outdoor activity.
The primary pollutant affecting Jefferson, Washington is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the Jefferson County area.
Jefferson, Washington averages 2 unhealthy air days per year. This is relatively low, making it a reasonable choice for asthma sufferers. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 21 (Good), outdoor exercise in Jefferson, Washington is generally safe year-round. Jefferson, Washington averages 2 days per year when athletes should move workouts indoors.