Median AQI
31
Good
North Carolina · County air quality · 2025
Martin County, North Carolina
Median AQI 31 (Good). 100.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 31
- Median AQI
- 100.0%
- Good-air days
- 0
- Unhealthy days
- 99%
- Cleaner than US counties
Martin County's 2025 annual median AQI is 31 (Good), with 100.0% Good days
According to the U.S. EPA Air Quality System, Martin County, North Carolina posted a 2025 median AQI of 31 (Good) across 289 monitored days, with 100.0% 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
- Martin County's 100.0% Good-day share places it cleaner than 99% of US counties in 2025.
- Closest median-AQI peer
- Athens County (83.4% Good, median AQI 31) is the closest nationwide median-AQI peer to Martin County.
- 2020–2025 trend
- Martin County's floor-qualifying Good-day share is stable from 2020 to 2025 (100.0% → 100.0%).
- Median AQI
- Median AQI: 31
The verdict
According to EPA Air Quality System monitoring data, Martin County's air is good on balance, among the cleanest 1% of US counties, a median AQI of 31 with 100.0% of 289 monitored days in the Good band, driven mainly by Ozone.
- 31
- median AQI · Good
- 100.0%
- days rated Good
- Ozone
- main pollutant
- 99%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 50.
Annual release change
What changed in the 2025 EPA annual release
- Martin County's peak single-day AQI fell from 61 to 50 between the 2024 and 2025 EPA annual releases, a change of -11 points.
Data updated August 2026
- Good · 289 d · 100.0%
How did Martin County's air break down in 2025?
Across 289 monitored days, 289 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 50 (Good).
EPA AQS →Air quality data from EPA Air Quality System (2025). 289 days monitored. Median AQI: 31 (Good).
Insights: Martin County, North Carolina. EPA monitors recorded a median Air Quality Index of 31 across 289 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 289 (100%) fell in the Good band (AQI 0–50), 0 (0%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 41, while the worst single-day peak hit 50 (Good). Residents averaged about 30.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (241 days), PM10 (48 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +0.0 points (measured against 240 monitored days in 2020 and 289 in 2025, so raw day counts are not comparable) and the median AQI moved -2 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 50, good but never Unhealthy. Nearby counties show comparable readings: Alexander (93.5% good, AQI 38); Avery (92.3% good, AQI 38); Buncombe (73.4% good, AQI 40); Caldwell (97.1% good, AQI 36); Carteret (96.2% good, AQI 35); Caswell (95.1% good, AQI 37).
Air Quality Summary
Good Days
100.0%
289 of 289 monitored days
25.0pp vs 75% target
Max AQI Recorded
50
Good
Health Grade
Excellent
90th-pct AQI 41
Martin County, Good days share 100.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Martin 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 (2025)
Distribution of 289 monitored days across EPA AQI categories.
Good
289
100%
Moderate
0
0%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Martin County.
- Ozone · 241 days · 83.4%
- PM10 · 48 days · 16.6%
Health Impact Assessment
Excellent
Martin County's air quality is rated Excellent based on 100.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 100.0% of monitored days in 2025, with a median AQI of 31. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 241 of 289 monitored days.
5-Year Air Quality Trend
Air quality is stable in Martin County. Highest Good-day share: 2025 (100.0%, 289 of 289 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 240 | 0 | 0 | 0 | 33 | 49 |
| 2021 | 291 | 5 | 0 | 0 | 32 | 74 |
| 2022 | 282 | 7 | 0 | 0 | 34 | 80 |
| 2023 | 230 | 14 | 0 | 0 | 36 | 77 |
| 2024 | 304 | 1 | 0 | 0 | 31 | 61 |
| 2025 | 289 | 0 | 0 | 0 | 31 | 50 |
How does Martin County compare?
How Martin County compares
Good-day share better than US avg
Martin County 100.0%
Athens County, Ohio 83.4%
US average 76.0%
Median AQI better than US avg
Martin County 31
Athens County, Ohio 31
US average 39
Unhealthy days / yr better than US avg
Martin County 0
Athens County, Ohio 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Martin County (31), not geographic neighbors.
Athens County, Ohio
Median AQI 31 · 83.4% Good-day share
Clackamas County, Oregon
Median AQI 31 · 87.6% Good-day share
Grant County, Oklahoma
Median AQI 31 · 82.3% Good-day share
Kent County, Rhode Island
Median AQI 31 · 92.8% Good-day share
Kootenai County, Idaho
Median AQI 31 · 77.8% Good-day share
Lake County, California
Median AQI 31 · 99.2% 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).
Carbon County, Wyoming
100.0% Good-day share · median AQI 8
Denali County, Alaska
99.7% Good-day share · median AQI 33
Solano County, California
99.2% Good-day share · median AQI 33
Liberty County, Florida
98.5% Good-day share · median AQI 33
Flagler County, Florida
98.1% Good-day share · median AQI 34
Elmore County, Alabama
97.9% Good-day share · median AQI 34
North Carolina counties on the map
Geographic containment only, other monitored counties in North Carolina, independent of AQI or pollutant match.
What Martin 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 31 means for exposure. Health guidance
- See how Martin County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Martin County with its North Carolina neighbours before drawing a conclusion about the region. All of North Carolina
Based on 289 EPA-monitored days in 2025; 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 Martin County, North Carolina? ▼
Martin County has a median Air Quality Index (AQI) of 31, rated "Good." 100.0% of monitored days (289 out of 289) had good air quality in 2025.
What is the main pollutant in Martin County? ▼
The primary pollutant in Martin County is Ozone (O3), which was the main AQI driver on 241 days (83% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Martin County have? ▼
In 2025, Martin County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 50.
Is the air quality in Martin County getting better or worse? ▼
Air quality in Martin County is stable across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2025 at 100.0% (289 of 289 days). Lowest qualifying Good-day share: 2023 at 94.3% (230 of 244 days).
What does AQI 31 mean for health? ▼
Martin County's median AQI of 31 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Martin County compare to other counties in North Carolina? ▼
Martin County has 100.0% good air days. Nearby counties in North Carolina: Alexander (93.5% good), Avery (92.3% good), Buncombe (73.4% good), Caldwell (97.1% good), Carteret (96.2% good), Caswell (95.1% good).
What is the 90th percentile AQI in Martin County? ▼
The 90th percentile AQI for Martin County is 41, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 50 (Good).
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 Martin County, North Carolina · 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.