Median AQI
43
Good
West Virginia · County air quality · 2025
Monongalia County, West Virginia
Median AQI 43 (Good). 79.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 43
- Median AQI
- 79.1%
- Good-air days
- 0
- Unhealthy days
- 50%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Monongalia County's air is good on balance, cleaner than the median US county, a median AQI of 43 with 79.1% of 129 monitored days in the Good band, driven mainly by Ozone.
- 43
- median AQI · Good
- 79.1%
- days rated Good
- Ozone
- main pollutant
- 50%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 105.
Data updated July 2026
- Good · 102 d · 79.1%
- Moderate · 26 d · 20.2%
- USG · 1 d · 0.8%
How did Monongalia County's air break down in 2025?
Across 129 monitored days, 102 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 105 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 129 days monitored. Median AQI: 43 (Good).
Insights: Monongalia County, West Virginia. EPA monitors recorded a median Air Quality Index of 43 across 129 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 102 (79%) fell in the Good band (AQI 0–50), 26 (20%) registered Moderate readings, and 1 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 63, while the worst single-day peak hit 105 (USG). Residents averaged about 23.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (100 days), PM2.5 (29 days). Across the 2020–2025 trend window, good days shifted by -146 and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 105, usg but never Unhealthy. Nearby counties show comparable readings: Berkeley (81.1% good, AQI 40); Brooke (79.3% good, AQI 35); Cabell (74.0% good, AQI 41); Greenbrier (89.3% good, AQI 42); Hancock (74.6% good, AQI 42); Harrison (73.3% good, AQI 32).
Air Quality Summary
Good Days
79.1%
102 of 129 monitored days
4.1pp vs 75% target
Max AQI Recorded
105
USG
Health Grade
Good
90th-pct AQI 63
Monongalia County, Good days share 79.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Monongalia 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 129 monitored days across EPA AQI categories.
Good
102
79%
Moderate
26
20%
USG
1
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 Monongalia County.
- Ozone · 100 days · 77.5%
- PM2.5 · 29 days · 22.5%
Health Impact Assessment
Good
Monongalia County's air quality is rated Good based on 79.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 79.1% of monitored days in 2025, with a median AQI of 43. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 100 of 129 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Monongalia County. Best year: 2022 (250 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 248 | 26 | 0 | 0 | 39 | 90 |
| 2021 | 225 | 57 | 0 | 0 | 39 | 80 |
| 2022 | 250 | 30 | 0 | 0 | 37 | 77 |
| 2023 | 227 | 49 | 0 | 1 | 42 | 169 |
| 2024 | 211 | 56 | 0 | 0 | 43 | 93 |
| 2025 | 102 | 26 | 1 | 0 | 43 | 105 |
How does Monongalia County compare?
How Monongalia County compares
Good-day share better than US avg
Monongalia County 79.1%
Berkeley County, West Virginia 81.1%
US average 76.5%
Median AQI worse than US avg
Monongalia County 43
Berkeley County, West Virginia 40
US average 38
Unhealthy days / yr about average
Monongalia County 0
Berkeley County, West Virginia 0
US average 0
Other Counties in West Virginia
Air quality comparison for nearby counties in West Virginia.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Monongalia 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 Monongalia 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 43 means for exposure. Health guidance
- See how Monongalia County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Monongalia County with its West Virginia neighbours before drawing a conclusion about the region. All of West Virginia
Based on 129 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 Monongalia County, West Virginia? ▼
Monongalia County has a median Air Quality Index (AQI) of 43, rated "Good." 79.1% of monitored days (102 out of 129) had good air quality in 2025.
What is the main pollutant in Monongalia County? ▼
The primary pollutant in Monongalia County is Ozone (O3), which was the main AQI driver on 100 days (78% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Monongalia County have? ▼
In 2025, Monongalia County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 105.
Is the air quality in Monongalia County getting better or worse? ▼
Air quality in Monongalia County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 250 good days. Worst year: 2025 with 102 good days.
What does AQI 43 mean for health? ▼
Monongalia 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 Monongalia County compare to other counties in West Virginia? ▼
Monongalia County has 79.1% good air days. Nearby counties in West Virginia: Berkeley (81.1% good), Brooke (79.3% good), Cabell (74.0% good), Greenbrier (89.3% good), Hancock (74.6% good), Harrison (73.3% good).
What is the 90th percentile AQI in Monongalia County? ▼
The 90th percentile AQI for Monongalia County is 63, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 105 (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.
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.