Median AQI
35
Good
Missouri · County air quality · 2025
Monroe County, Missouri
Median AQI 35 (Good). 94.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 35
- Median AQI
- 94.0%
- Good-air days
- 0
- Unhealthy days
- 90%
- Cleaner than US counties
Monroe County's 2025 annual median AQI is 35 (Good), with 94.0% Good days
According to the U.S. EPA Air Quality System, Monroe County, Missouri posted a 2025 median AQI of 35 (Good) across 365 monitored days, with 94.0% 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
- Monroe County's 94.0% Good-day share places it cleaner than 90% of US counties in 2025.
- Closest median-AQI peer
- Atascosa County (76.0% Good, median AQI 35) is the closest nationwide median-AQI peer to Monroe County.
- 2020–2025 trend
- Monroe County's floor-qualifying Good-day share is worsening from 2020 to 2025 (98.4% → 94.0%).
- Median AQI
- Median AQI: 35
The verdict
According to EPA Air Quality System monitoring data, Monroe County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 35 with 94.0% of 365 monitored days in the Good band, driven mainly by Ozone.
- 35
- median AQI · Good
- 94.0%
- days rated Good
- Ozone
- main pollutant
- 90%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 97.
Annual release change
What changed in the 2025 EPA annual release
- Monroe County's Good-day share fell from 97.5% to 94.0% between the 2024 and 2025 EPA annual releases, a change of -3.5 percentage points.
- Monroe County's peak single-day AQI rose from 84 to 97 between the 2024 and 2025 EPA annual releases, a change of +13 points.
Data updated August 2026
- Good · 343 d · 94.0%
- Moderate · 22 d · 6.0%
How did Monroe County's air break down in 2025?
Across 365 monitored days, 343 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). 365 days monitored. Median AQI: 35 (Good).
Insights: Monroe County, Missouri. EPA monitors recorded a median Air Quality Index of 35 across 365 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 343 (94%) fell in the Good band (AQI 0–50), 22 (6%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 47, while the worst single-day peak hit 97 (Moderate). Residents averaged about 28.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (353 days), PM10 (11 days), NO2 (1 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -4.4 points 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 97, moderate but never Unhealthy. Nearby counties show comparable readings: Andrew (86.9% good, AQI 40); Boone (93.2% good, AQI 37); Buchanan (56.4% good, AQI 46); Callaway (89.6% good, AQI 41); Cass (77.6% good, AQI 41); Cedar (81.6% good, AQI 39).
Air Quality Summary
Good Days
94.0%
343 of 365 monitored days
19.0pp vs 75% target
Max AQI Recorded
97
Moderate
Health Grade
Excellent
90th-pct AQI 47
Monroe County, Good days share 94.0%
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 365 monitored days across EPA AQI categories.
Good
343
94%
Moderate
22
6%
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 · 353 days · 96.7%
- PM10 · 11 days · 3.0%
- NO₂ · 1 days · 0.3%
Health Impact Assessment
Excellent
Monroe County's air quality is rated Excellent based on 94.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 94.0% of monitored days in 2025, with a median AQI of 35. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 353 of 365 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Monroe County. Highest Good-day share: 2022 (99.7%, 364 of 365 monitored 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 | 343 | 22 | 0 | 0 | 35 | 97 |
How does Monroe County compare?
How Monroe County compares
Good-day share better than US avg
Monroe County 94.0%
Atascosa County, Texas 76.0%
US average 76.0%
Median AQI better than US avg
Monroe County 35
Atascosa County, Texas 35
US average 39
Unhealthy days / yr better than US avg
Monroe County 0
Atascosa County, Texas 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Monroe County (35), not geographic neighbors.
Atascosa County, Texas
Median AQI 35 · 76.0% Good-day share
Benzie County, Michigan
Median AQI 35 · 91.1% Good-day share
Berkeley County, South Carolina
Median AQI 35 · 93.3% Good-day share
Boone County, Indiana
Median AQI 35 · 89.7% Good-day share
Brazoria County, Texas
Median AQI 35 · 80.8% Good-day share
Caroline County, Virginia
Median AQI 35 · 96.7% 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).
Dutchess County, New York
94.0% Good-day share · median AQI 34
Leavenworth County, Kansas
94.0% Good-day share · median AQI 34
Rockbridge County, Virginia
93.9% Good-day share · median AQI 36
Okaloosa County, Florida
93.9% Good-day share · median AQI 36
St. James County, Louisiana
93.9% Good-day share · median AQI 33
Indian River County, Florida
94.1% Good-day share · median AQI 37
Missouri counties on the map
Geographic containment only, other monitored counties in Missouri, independent of AQI or pollutant match.
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 35 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 365 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 Monroe County, Missouri? ▼
Monroe County has a median Air Quality Index (AQI) of 35, rated "Good." 94.0% of monitored days (343 out of 365) 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 353 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 across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2022 at 99.7% (364 of 365 days). Lowest qualifying Good-day share: 2023 at 87.1% (317 of 364 days).
What does AQI 35 mean for health? ▼
Monroe County's median AQI of 35 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Monroe County compare to other counties in Missouri? ▼
Monroe County has 94.0% good air days. Nearby counties in Missouri: Andrew (86.9% good), Boone (93.2% good), Buchanan (56.4% good), Callaway (89.6% good), Cass (77.6% good), Cedar (81.6% good).
What is the 90th percentile AQI in Monroe County? ▼
The 90th percentile AQI for Monroe County is 47, 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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Monroe County, Missouri · 2020–2025
Share this annual record
Send the source-year summary or download its ready-to-use data card.
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.