Median AQI
37
Good
Missouri · County air quality · 2025
Monroe County, Missouri
Median AQI 37 (Good). 89.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 37
- Median AQI
- 89.9%
- Good-air days
- 0
- Unhealthy days
- 75%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Monroe County's air is good on balance, cleaner than most US counties, a median AQI of 37 with 89.9% of 148 monitored days in the Good band, driven mainly by Ozone.
- 37
- median AQI · Good
- 89.9%
- days rated Good
- Ozone
- main pollutant
- 75%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 97.
Data updated July 2026
- Good · 133 d · 89.9%
- Moderate · 15 d · 10.1%
How did Monroe County's air break down in 2025?
Across 148 monitored days, 133 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 97 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 148 days monitored. Median AQI: 37 (Good).
Insights: Monroe County, Missouri. EPA monitors recorded a median Air Quality Index of 37 across 148 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 133 (90%) fell in the Good band (AQI 0–50), 15 (10%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 51, while the worst single-day peak hit 97 (Moderate). Residents averaged about 27.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (143 days), PM10 (5 days). Across the 2020–2025 trend window, good days shifted by -227 and the median AQI moved +6 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 97, moderate but never Unhealthy. Nearby counties show comparable readings: Andrew (84.3% good, AQI 42); Boone (89.1% good, AQI 41); Buchanan (64.2% good, AQI 39); Callaway (85.6% good, AQI 42); Cass (82.2% good, AQI 41); Cedar (81.8% good, AQI 40).
Air Quality Summary
Good Days
89.9%
133 of 148 monitored days
14.9pp vs 75% target
Max AQI Recorded
97
Moderate
Health Grade
Good
90th-pct AQI 51
Monroe County, Good days share 89.9%
National avg
Share of monitored days at AQI 0-50 (Good band).
Monroe 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 148 monitored days across EPA AQI categories.
Good
133
90%
Moderate
15
10%
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 Monroe County.
- Ozone · 143 days · 96.6%
- PM10 · 5 days · 3.4%
Health Impact Assessment
Good
Monroe County's air quality is rated Good based on 89.9% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 89.9% of monitored days in 2025, with a median AQI of 37. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 143 of 148 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Monroe County. Best year: 2022 (364 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 360 | 6 | 0 | 0 | 31 | 84 |
| 2021 | 359 | 6 | 0 | 0 | 32 | 71 |
| 2022 | 364 | 1 | 0 | 0 | 34 | 52 |
| 2023 | 317 | 44 | 3 | 0 | 38 | 119 |
| 2024 | 350 | 9 | 0 | 0 | 36 | 84 |
| 2025 | 133 | 15 | 0 | 0 | 37 | 97 |
How does Monroe County compare?
How Monroe County compares
Good-day share better than US avg
Monroe County 89.9%
Andrew County, Missouri 84.3%
US average 76.5%
Median AQI better than US avg
Monroe County 37
Andrew County, Missouri 42
US average 38
Unhealthy days / yr about average
Monroe County 0
Andrew County, Missouri 0
US average 0
Other Counties in Missouri
Air quality comparison for nearby counties in Missouri.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Monroe County.
Alachua County, Florida
AQI 37 · 90.1% good
Beltrami County, Minnesota
AQI 37 · 88.8% good
Benewah County, Idaho
AQI 37 · 74.6% good
Brevard County, Florida
AQI 37 · 89.7% good
Brown County, Indiana
AQI 37 · 94.5% good
Brown County, Wisconsin
AQI 37 · 79.0% good
What Monroe 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 37 means for exposure. Health guidance
- See how Monroe County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Monroe County with its Missouri neighbours before drawing a conclusion about the region. All of Missouri
Based on 148 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 Monroe County, Missouri? ▼
Monroe County has a median Air Quality Index (AQI) of 37, rated "Good." 89.9% of monitored days (133 out of 148) had good air quality in 2025.
What is the main pollutant in Monroe County? ▼
The primary pollutant in Monroe County is Ozone (O3), which was the main AQI driver on 143 days (97% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Monroe County have? ▼
In 2025, Monroe County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 97.
Is the air quality in Monroe County getting better or worse? ▼
Air quality in Monroe County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 364 good days. Worst year: 2025 with 133 good days.
What does AQI 37 mean for health? ▼
Monroe County's median AQI of 37 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 Monroe County compare to other counties in Missouri? ▼
Monroe County has 89.9% good air days. Nearby counties in Missouri: Andrew (84.3% good), Boone (89.1% good), Buchanan (64.2% good), Callaway (85.6% good), Cass (82.2% good), Cedar (81.8% good).
What is the 90th percentile AQI in Monroe County? ▼
The 90th percentile AQI for Monroe County is 51, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 97 (Moderate).
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.