Median AQI
44
Good
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
The verdict
According to EPA Air Quality System monitoring data, Johnston County's air is good on balance, more polluted than the median US county, a median AQI of 44 with 74.7% of 257 monitored days in the Good band, driven mainly by Ozone.
- 44
- median AQI · Good
- 74.7%
- days rated Good
- Ozone
- main pollutant
- 33%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 119.
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 →Air quality data from EPA Air Quality System (2024). 257 days monitored. Median AQI: 44 (Good).
Insights: Johnston County, Oklahoma. EPA monitors recorded a median Air Quality Index of 44 across 257 measured days in 2024, earning a Good classification and a Moderate health grade. Of those days, 192 (75%) fell in the Good band (AQI 0–50), 62 (24%) registered Moderate readings, and 3 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 71, while the worst single-day peak hit 119 (USG). Residents averaged about 22.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (257 days). Across the 2020–2024 trend window, the share of monitored days rated Good shifted by -17.7 points (measured against 289 monitored days in 2020 and 257 in 2024, so raw day counts are not comparable) and the median AQI moved +6 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2024 window was AQI 119, usg but never Unhealthy. Nearby counties show comparable readings: Adair (55.8% good, AQI 48); Canadian (79.3% good, AQI 43); Carter (81.6% good, AQI 32); Cleveland (56.9% good, AQI 48); Comanche (66.8% good, AQI 44); Creek (80.6% good, AQI 42).
Air Quality Summary
Good Days
74.7%
192 of 257 monitored days
-0.3pp vs 75% target
Max AQI Recorded
119
USG
Health Grade
Moderate
90th-pct AQI 71
Johnston County, Good days share 74.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Johnston County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2024)
Distribution of 257 monitored days across EPA AQI categories.
Good
192
75%
Moderate
62
24%
USG
3
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Johnston County.
- Ozone · 257 days · 100.0%
Health Impact Assessment
Moderate
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
Good-day share worse than US avg
Johnston County 74.7%
Yancey County, North Carolina 81.9%
US average 76.0%
Median AQI worse than US avg
Johnston County 44
Yancey County, North Carolina 44
US average 39
Unhealthy days / yr better than US avg
Johnston County 0
Yancey County, North Carolina 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Johnston County (44), not geographic neighbors.
Yancey County, North Carolina
Median AQI 44 · 81.9% Good-day share
Pontotoc County, Oklahoma
Median AQI 43 · 71.6% Good-day share
Jefferson County, Oklahoma
Median AQI 42 · 81.0% Good-day share
Rio Blanco County, Colorado
Median AQI 46 · 72.7% Good-day share
Santa Clara County, California
Median AQI 47 · 55.4% Good-day share
Contra Costa County, California
Median AQI 48 · 53.5% Good-day share
Same primary pollutant: Ozone
Ozone led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Weston County, Wyoming
87.7% Good-day share · median AQI 39
Big Horn County, Wyoming
89.2% Good-day share · median AQI 39
Sumter County, Georgia
93.4% Good-day share · median AQI 38
Columbia County, Georgia
94.2% Good-day share · median AQI 36
Chattooga County, Georgia
96.3% Good-day share · median AQI 39
Oklahoma counties on the map
Geographic containment only, other monitored counties in Oklahoma, independent of AQI or pollutant match.
What Johnston County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 44 means for exposure. Health guidance
- See how Johnston County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Johnston County with its Oklahoma neighbours before drawing a conclusion about the region. All of Oklahoma
Based on 257 EPA-monitored days in 2024; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Johnston County, Oklahoma? ▼
Johnston County has a median Air Quality Index (AQI) of 44, rated "Good." 74.7% of monitored days (192 out of 257) had good air quality in 2024.
What is the main pollutant in Johnston County? ▼
The primary pollutant in Johnston County is Ozone (O3), which was the main AQI driver on 257 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Johnston County have? ▼
In 2024, Johnston County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 119.
Is the air quality in Johnston County getting better or worse? ▼
Air quality in Johnston County is worsening across floor-qualifying years (2020-2024); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 92.4% (267 of 289 days). Lowest qualifying Good-day share: 2023 at 67.5% (166 of 246 days).
What does AQI 44 mean for health? ▼
Johnston County's median AQI of 44 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Johnston County compare to other counties in Oklahoma? ▼
Johnston County has 74.7% good air days. Nearby counties in Oklahoma: Adair (55.8% good), Canadian (79.3% good), Carter (81.6% good), Cleveland (56.9% good), Comanche (66.8% good), Creek (80.6% good).
What is the 90th percentile AQI in Johnston County? ▼
The 90th percentile AQI for Johnston County is 71, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 119 (USG).
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
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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.