Metro area air quality · 2025

Mount Vernon, IL

Median AQI 43 (Good). 66.5% of monitored days rated Good across this metro's EPA monitoring network.

43
Median AQI
66.5%
Good-air days
0
Unhealthy days
37%
Cleaner than US metros

Aggregated from EPA Air Quality System (2025), 269 monitored days. EPA AQS →

The verdict

The Mount Vernon, IL metro runs good on the EPA scale, more polluted than the median US metro, a median AQI of 43 with 66.5% of 269 monitored days in the Good band.

43
median AQI · Good
66.5%
days rated Good
37%
cleaner than US metros
98
worst single reading

No day crossed into the Unhealthy tier across the metro's monitors in 2025.

Insights: Mount Vernon, IL metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 43 over 269 measured days in 2025, which corresponds to a Good band and a Moderate metro-wide health grade. The monitored-day split lands at 179 Good days (67%), 90 Moderate (33%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 62 while the highest single-day reading hit 98 (Moderate). Metro residents averaged roughly 20.0 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -44 and the median AQI moved -3 points, which classifies the multi-year trajectory as improving. The metro avoided any Unhealthy-tier days entirely, an outcome that typically reflects favorable wind patterns, lower industrial density, or effective regional emission controls. Metros with comparable AQI profiles include Allentown-Bethlehem-Easton, PA-NJ (65.6% good, AQI 43); Amarillo, TX (75.7% good, AQI 43); Ashtabula, OH (81.2% good, AQI 43).

Air Quality Summary

Median AQI

43

Good

Good Days

66.5%

179 of 269 days

Max AQI

98

Moderate

Health Grade

Moderate

90th pct: 62

AQI Day Breakdown (2025)

Distribution of 269 monitored days across EPA AQI categories.

Good

179

67%

Moderate

90

33%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Mount Vernon, IL metro area's air quality is rated Moderate based on 66.5% good air days. No unhealthy air days were recorded in 2025.

Air quality is generally acceptable. Unusually sensitive people should monitor real-time conditions at AirNow.gov during high-pollution events.

How does the Mount Vernon, IL metro compare?

How Mount Vernon, IL compares

Good-day share worse than US avg
Mount Vernon, IL 66.5%
Allentown-Bethlehem-Easton, PA-NJ 65.6%
US average 71.3%
Median AQI worse than US avg
Mount Vernon, IL 43
Allentown-Bethlehem-Easton, PA-NJ 43
US average 41
Unhealthy days / yr better than US avg
Mount Vernon, IL 0
Allentown-Bethlehem-Easton, PA-NJ 0
US average 1

5-Year Air Quality Trend

Air quality is improving in the Mount Vernon, IL metro. Best year: 2024 (236 good days).

Year Good Moderate Unhealthy Median AQI
2020 223 129 0 46
2021 207 155 0 48
2022 227 138 0 45
2023 213 141 1 46
2024 236 129 0 44
2025 179 90 0 43

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Mount Vernon, IL.

Allentown-Bethlehem-Easton, PA-NJ

AQI 43 · 65.6% good

43

Amarillo, TX

AQI 43 · 75.7% good

43

Ashtabula, OH

AQI 43 · 81.2% good

43

College Station-Bryan, TX

AQI 43 · 63.4% good

43

Fallon, NV

AQI 43 · 81.0% good

43

Gillette, WY

AQI 43 · 77.3% good

43

More Air Quality Data

Explore EPA air quality rankings and guides across U.S. metros and counties.

Cleanest Metro Areas

U.S. metros ranked by their share of Good air-quality days.

Worst Air Quality

Counties and metros with the most unhealthy air days.

All Metro Areas

Annual AQI by CBSA for every monitored U.S. metro area.

Best and Worst City Air

What drives urban air quality and how metro areas compare.

Air Quality Guides

Frequently Asked Questions

What is the air quality in the Mount Vernon, IL metro area? ▼
The Mount Vernon, IL metro area has a median Air Quality Index (AQI) of 43, rated "Good." 66.5% of monitored days (179 out of 269) had good air quality in 2025.
How many unhealthy air days does Mount Vernon, IL have? ▼
In 2025, the Mount Vernon, IL metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 98.
Is air quality in Mount Vernon, IL getting better or worse? ▼
Air quality in the Mount Vernon, IL metro is improving based on 5-year trends (2020-2025). Best year: 2024 with 236 good days. Worst year: 2025 with 179 good days.
What does AQI 43 mean for health? ▼
An AQI of 43 is "Good", air quality is satisfactory and poses little or no health risk. This is the best category on the EPA's AQI scale.
What is the 90th percentile AQI for Mount Vernon, IL? ▼
The 90th percentile AQI for the Mount Vernon, IL metro area is 62, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 98 (Moderate).
How does Mount Vernon, IL compare to other metro areas? ▼
The Mount Vernon, IL metro has 66.5% good air days. Similar metros: Allentown-Bethlehem-Easton, PA-NJ (65.6% good), Amarillo, TX (75.7% good), Ashtabula, OH (81.2% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset, 2020–2025. See our methodology for how AQI, median, and coverage figures are computed.

Read our methodology , how this data is sourced, computed, and verified.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by CBSA summary files (metro-level) · 2020–2025

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.