Median AQI
43
Good
Kansas · County air quality · 2025
Johnson County, Kansas
Median AQI 43 (Good). 71.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 43
- Median AQI
- 71.8%
- Good-air days
- 1
- Unhealthy days
- 35%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Johnson County's air is good on balance, more polluted than the median US county, a median AQI of 43 with 71.8% of 181 monitored days in the Good band, driven mainly by Ozone.
- 43
- median AQI · Good
- 71.8%
- days rated Good
- Ozone
- main pollutant
- 35%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 188.
Data updated July 2026
- Good · 130 d · 71.8%
- Moderate · 50 d · 27.6%
- Unhealthy · 1 d · 0.6%
How did Johnson County's air break down in 2025?
Across 181 monitored days, 130 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 188 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 43 (Good).
Insights: Johnson County, Kansas. EPA monitors recorded a median Air Quality Index of 43 across 181 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 130 (72%) fell in the Good band (AQI 0–50), 50 (28%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 60, while the worst single-day peak hit 188 (Unhealthy). Residents averaged about 21.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (103 days), PM2.5 (76 days), PM10 (2 days). Across the 2020–2025 trend window, good days shifted by -120 and the median AQI moved +2 points, placing the multi-year trajectory at improving. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Chase (88.9% good, AQI 22); Douglas (90.7% good, AQI 41); Ford (89.4% good, AQI 26); Leavenworth (93.9% good, AQI 36); Neosho (73.5% good, AQI 43); Sedgwick (58.6% good, AQI 48).
Air Quality Summary
Good Days
71.8%
130 of 181 monitored days
-3.2pp vs 75% target
Max AQI Recorded
188
Unhealthy
Health Grade
Moderate
90th-pct AQI 60
Johnson County, Good days share 71.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Johnson County, Unhealthy-or-worse share 0.6%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 181 monitored days across EPA AQI categories.
Good
130
72%
Moderate
50
28%
USG
0
0%
Unhealthy
1
1%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Johnson County.
- Ozone · 103 days · 56.9%
- PM2.5 · 76 days · 42.0%
- PM10 · 2 days · 1.1%
Health Impact Assessment
Moderate
Johnson County's air quality is rated Moderate based on 71.8% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 0 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 188. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 103 of 181 monitored days.
5-Year Air Quality Trend
Air quality is improving in Johnson County. Best year: 2024 (257 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 250 | 114 | 1 | 0 | 41 | 117 |
| 2021 | 207 | 153 | 4 | 0 | 46 | 138 |
| 2022 | 227 | 137 | 1 | 0 | 44 | 115 |
| 2023 | 189 | 166 | 7 | 3 | 49 | 165 |
| 2024 | 257 | 109 | 0 | 0 | 44 | 80 |
| 2025 | 130 | 50 | 0 | 1 | 43 | 188 |
How does Johnson County compare?
How Johnson County compares
Good-day share worse than US avg
Johnson County 71.8%
Chase County, Kansas 88.9%
US average 76.5%
Median AQI worse than US avg
Johnson County 43
Chase County, Kansas 22
US average 38
Unhealthy days / yr worse than US avg
Johnson County 1
Chase County, Kansas 0
US average 0
Other Counties in Kansas
Air quality comparison for nearby counties in Kansas.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Johnson County.
Allegan County, Michigan
AQI 43 · 71.2% good
Allen County, Ohio
AQI 43 · 65.9% good
Ashtabula County, Ohio
AQI 43 · 81.2% good
Bell County, Kentucky
AQI 43 · 63.5% good
Boise County, Idaho
AQI 43 · 72.9% good
Brazos County, Texas
AQI 43 · 63.4% good
What Johnson County's air means for you
On most days the air here is fine, but Ozone drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 43 means for exposure. Health guidance
- See how Johnson County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Johnson County with its Kansas neighbours before drawing a conclusion about the region. All of Kansas
Based on 181 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Johnson County, Kansas? ▼
Johnson County has a median Air Quality Index (AQI) of 43, rated "Good." 71.8% of monitored days (130 out of 181) had good air quality in 2025.
What is the main pollutant in Johnson County? ▼
The primary pollutant in Johnson County is Ozone (O3), which was the main AQI driver on 103 days (57% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Johnson County have? ▼
In 2025, Johnson County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 188.
Is the air quality in Johnson County getting better or worse? ▼
Air quality in Johnson County is improving based on 5-year trends (2020-2025). Best year: 2024 with 257 good days. Worst year: 2025 with 130 good days.
What does AQI 43 mean for health? ▼
Johnson County's median AQI of 43 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Johnson County compare to other counties in Kansas? ▼
Johnson County has 71.8% good air days. Nearby counties in Kansas: Chase (88.9% good), Douglas (90.7% good), Ford (89.4% good), Leavenworth (93.9% good), Neosho (73.5% good), Sedgwick (58.6% good).
What is the 90th percentile AQI in Johnson County? ▼
The 90th percentile AQI for Johnson County is 60, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 188 (Unhealthy).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.