Oklahoma · County air quality · 2024
Johnston County, Oklahoma
Median AQI 44 (Good). 74.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 44
- Median AQI
- 74.7%
- Good-air days
- 0
- Unhealthy days
- 33%
- Cleaner than US counties
Johnston County's 2024 annual median AQI is 44 (Good), with 74.7% Good days
According to the U.S. EPA Air Quality System, Johnston County, Oklahoma posted a 2024 median AQI of 44 (Good) across 257 monitored days, with 74.7% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Johnston County's 74.7% Good-day share places it cleaner than 33% of US counties in 2024.
- Closest median-AQI peer
- Yancey County (81.9% Good, median AQI 44) is the closest nationwide median-AQI peer to Johnston County.
- 2020–2024 trend
- Johnston County's floor-qualifying Good-day share is worsening from 2020 to 2024 (92.4% → 74.7%).
- Median AQI
- Median AQI: 44
According to the 2024 EPA AQS county release on PlainAirData, Johnston County, Oklahoma ranks #10 of 15 by median AQI (44) and #10 by good-day share (74.7%). San Mateo County, California is #1 of 15 by median AQI (27, 88.1% Good days) at good-day-share #5 ≠ Chattooga County, Georgia #1 by good-day share (96.3%, median AQI 39) at median-AQI #5.
Annual release change
What changed in the 2024 EPA annual release
- Johnston County's Good-day share rose from 67.5% to 74.7% between the 2023 and 2024 EPA annual releases, a change of +7.2 percentage points.
- Johnston County's peak single-day AQI fell from 161 to 119 between the 2023 and 2024 EPA annual releases, a change of -42 points.
- Johnston County's Unhealthy-category days fell from 1 to 0 between the 2023 and 2024 EPA annual releases, a change of -1 days.
Data updated August 2026
- Good · 192 d · 74.7%
- Moderate · 62 d · 24.1%
- USG · 3 d · 1.2%
How did Johnston County's air break down in 2024?
Across 257 monitored days, 192 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 119 (USG).
EPA AQS →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Johnston County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2024. Johnston County's Good-day share is 74.7% - cleaner than 33% of that comparison set.
Johnston County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
74.7% 33rd percentile higher than 33% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2024
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Johnston County.
- Ozone · 257 days · 100.0%
2024 daily-monitor rhythm in Johnston County
Month-by-month median AQI from EPA day-level county monitors (257 reported days in 2024). Oct posted the highest typical readings (median AQI 51, peak 119); Nov was cleanest at median 35. Summer months (Jun–Aug) averaged median AQI 46 vs 37 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–2024792 daily readings show a recurring local pattern: Aug has the highest matched-month median AQI (53), while Dec is lowest (27). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Johnston County's air quality is rated Moderate based on 74.7% good air days. No unhealthy air days were recorded in 2024.
Air quality was acceptable on 74.7% of monitored days in 2024, with a median AQI of 44. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 257 of 257 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Johnston County. Highest Good-day share: 2020 (92.4%, 267 of 289 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 267 | 22 | 0 | 0 | 38 | 97 |
| 2023 | 166 | 75 | 4 | 1 | 46 | 161 |
| 2024 | 192 | 62 | 3 | 0 | 44 | 119 |
How does Johnston County compare?
How Johnston County compares
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Johnston County, Oklahoma · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.