Is the Air Quality Good in Johnson, Wyoming?
Mostly — air quality in Johnson, Wyoming is fair, not pristine. The city earns a Grade of C (fair) on a 5-year median AQI of 40 (Good), with 8 unhealthy-air days over five years (about 2 per year). Healthy adults are fine most of the time, but sensitive groups should watch the daily forecast.
Who Can Safely Breathe the Air in Johnson, Wyoming?
Healthy adults can continue normal outdoor activity in most weather, but should pay attention to AQI alerts during the worst pollution windows. People with asthma, heart disease, or pregnancy should reduce prolonged or intense outdoor exertion on flagged days, and consider running an indoor HEPA air cleaner during peak season. Because ozone peaks in the afternoon on hot sunny days, plan outdoor exercise for early morning or after sunset on bad-air days.
Across the past five years, this area has logged just 8 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 2 days per year, or roughly one every other month. That is a low count by national standards.
Johnson, Wyoming Air Quality Snapshot
| Air Quality Grade | C50/100 |
| 5-Year Median AQI | 40 (Good) |
| Most Recent Median AQI (2023) | 40 (Good) |
| Dominant Pollutant | Ground-Level Ozone |
| 10-Year Trend | Worsening (+3.97 AQI/yr) |
| Unhealthy Days (last 5 yr) | 8 |
| National Rank (cleanest = #1) | #474 of 1,020 (46th cleanest percentile) |
| Wyoming Rank | #7 of 18 |
What Does the C Grade Mean?
Johnson, Wyoming earns a C — air quality is fair, but not great. With a 5-year median AQI of 40, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.
Johnson, Wyoming's 5-year median AQI of 40 is right around the national average of 41 across the 1,020 monitored U.S. cities tracked here. Within Wyoming, Johnson, Wyoming runs more polluted than the state average of 37 — local sources or geography are concentrating pollution above the state's typical reading.
For context within Wyoming: Carbon, Wyoming currently holds the state's cleanest grade (A, AQI 16), while Lincoln, Wyoming sits at the bottom (C, AQI 29).
What's in Johnson, Wyoming's Air?
The dominant pollutant in Johnson, Wyoming is Ground-Level Ozone. Ground-level ozone forms when sunlight reacts with vehicle exhaust and industrial emissions. It is worst on hot, sunny, stagnant summer days. Ozone irritates the lungs, triggers asthma attacks, and reduces lung function — even healthy adults can feel chest tightness and shortness of breath after exercising in elevated ozone.
Days by Dominant Pollutant (2023)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Ground-Level Ozone | 350 | 96% |
| Coarse Particulate Matter (PM10) | 12 | 3% |
| Nitrogen Dioxide | 2 | 1% |
Is the Air Getting Better or Worse?
Air quality in Johnson, Wyoming has been getting worse over the past decade, with median AQI climbing by roughly 4.0 points per year. That bucks the national trend of broad improvement, and most often reflects either growing wildfire smoke exposure (particularly across the West) or rising local emissions from population and freight growth.
In 2014, Johnson, Wyoming posted a median AQI of 8. By 2023 that figure was 40 — a rise of 32 AQI points dirtier across 8 years of EPA records.
Year-by-Year AQI in Johnson, Wyoming
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 8 | 111 | 0 | PM2.5 |
| 2015 | 8 | 56 | 0 | PM2.5 |
| 2018 | 39 | 190 | 0 | Ozone |
| 2019 | 40 | 345 | 0 | Ozone |
| 2020 | 40 | 337 | 0 | Ozone |
| 2021 | 40 | 304 | 7 | Ozone |
| 2022 | 39 | 350 | 1 | Ozone |
| 2023 | 40 | 351 | 0 | Ozone |
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
More about Johnson, Wyoming
Johnson, Wyoming has an Air Quality Grade of C (fair) with a 5-year median AQI of 40. The dominant pollutant is Ground-Level Ozone, and air quality has been worsening over the past decade.
The data source behind this answer is the EPA Air Quality System (AQS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
A practical caveat: the headline answer above reflects the most recent the EPA Air Quality System (AQS) vintage; underlying data is often revised for months after first publication, and the right reference for any specific decision is whichever vintage is current at the time of the decision. The as-of date is stamped on every page.
Source: EPA Outdoor Air Quality Data, 2026.