Jefferson, Colorado Air Quality
Jefferson County, Colorado (CO)
→ Stableover 10 years
How Jefferson, Colorado Air Quality Compares
Jefferson, Colorado's median AQI of 49is 20% worse than the national average of 41. Residents experience an average of 29 unhealthy air days per year, above the national threshold for concern. The primary pollutant of concern is Ground-Level Ozone.
10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days).
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 | 49 | 90 | 143 | 206 | 141 | 18 | Ozone |
| 2022 | 47 | 97 | 166 | 234 | 100 | 31 | Ozone |
| 2021 | 47 | 115 | 172 | 222 | 88 | 55 | Ozone |
| 2020 | 46 | 90 | 161 | 231 | 108 | 27 | Ozone |
| 2019 | 46 | 87 | 129 | 238 | 111 | 16 | Ozone |
| 2018 | 46 | 101 | 151 | 229 | 99 | 37 | Ozone |
| 2017 | 47 | 93 | 136 | 214 | 123 | 28 | Ozone |
| 2016 | 46 | 87 | 159 | 245 | 101 | 20 | Ozone |
| 2015 | 45 | 84 | 164 | 244 | 104 | 17 | Ozone |
| 2014 | 46 | 84 | 140 | 228 | 121 | 16 | Ozone |
What This Means for Jefferson County Residents
Jefferson, Colorado has received an Air Quality Grade of D (46/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 49 falls in the "Good" range.
The primary pollutant affecting this area is Ground-Level Ozone. Over the past 5 years, this area has averaged 29 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.
Related Cities in Colorado
Frequently Asked Questions
Jefferson, Colorado has a current median AQI of 49, which falls in the "Good" range. The area has received an Air Quality Grade of D (46/100) based on 10 years of EPA monitoring data.
Air quality in Jefferson, Colorado is stable over the past decade. The median AQI has changed by +3 points from 2014 to 2023.
Jefferson, Colorado averages 29 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, Colorado is Ground-Level Ozone. This is the dominant contributor to elevated AQI readings in the Jefferson County area.
Jefferson, Colorado averages 29 unhealthy air days per year. With frequent unhealthy air days, asthma patients should use a HEPA air purifier indoors and check AQI before any outdoor activity. The primary pollutant is Ground-Level Ozone, which is a known asthma trigger.
With a median AQI of 49 (Good), outdoor exercise in Jefferson, Colorado is generally safe year-round. Jefferson, Colorado averages 29 days per year when athletes should move workouts indoors.
The this entity record above pulls directly from the EPA Air Quality System (AQS). What follows is the per-entity context — how this entity sits in the broader U.S. air quality and pollution monitoring distribution and which underlying factors drive the headline numbers.
The methodology behind every numeric value on this page is publicly documented on the the EPA Air Quality System (AQS) portal and described in detail on this site’s methodology page. Refresh cadence varies by underlying series; the page surfaces the as-of date for each number so readers can trace any figure back to the source release.
For readers using this page as a decision input, the related-entity pages elsewhere on the site provide the comparison set. The most useful comparison for this entity is typically a peer within U.S. counties and states with similar size, similar exposure, or similar geography — not the national-level summary alone.