Metro area air quality · 2024

Evanston, WY

Median AQI 7 (Good). 100.0% of monitored days rated Good across this metro's EPA monitoring network.

7
Median AQI
100.0%
Good-air days
0
Unhealthy days
99%
Cleaner than US metros

Aggregated from EPA Air Quality System (2024), 297 monitored days. EPA AQS → · NOAA →

Insights: Evanston, WY metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 7 over 297 measured days in 2024, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 297 Good days (100%), 0 Moderate (0%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 17 while the highest single-day reading hit 44 (Good). Metro residents averaged roughly 30.0 clean-air days per 30-day window across the reporting year.

Across the 2020–2024 trend window, good days shifted by -26 and the median AQI moved -33 points, which classifies the multi-year trajectory as worsening. 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 Pierre, SD (93.7% good, AQI 8); Mayaguez, PR (100.0% good, AQI 11); Ponce, PR (94.3% good, AQI 3).

Air Quality Summary

Median AQI

7

Good

Good Days

100.0%

297 of 297 days

Max AQI

44

Good

Health Grade

Excellent

90th pct: 17

AQI Day Breakdown (2024)

Distribution of 297 monitored days across EPA AQI categories.

Good

297

100%

Moderate

0

0%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Excellent

The Evanston, WY metro area's air quality is rated Excellent based on 100.0% good air days. No unhealthy air days were recorded in 2024.

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

How does the Evanston, WY metro compare?

How Evanston, WY compares

Good-day share better than US avg
Evanston, WY 100.0%
Pierre, SD 93.7%
US average 70.2%
Median AQI better than US avg
Evanston, WY 7
Pierre, SD 8
US average 41
Unhealthy days / yr better than US avg
Evanston, WY 0
Pierre, SD 0
US average 1

5-Year Air Quality Trend

Air quality is worsening in the Evanston, WY metro. Best year: 2023 (365 good days).

Year Good Moderate Unhealthy Median AQI
2020 323 41 0 40
2021 361 3 0 7
2022 363 2 0 7
2023 365 0 0 6
2024 297 0 0 7

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Evanston, WY.

Pierre, SD

AQI 8 · 93.7% good

8

Mayaguez, PR

AQI 11 · 100.0% good

11

Ponce, PR

AQI 3 · 94.3% good

3

Houghton, MI

AQI 12 · 98.3% good

12

Salem, OH

AQI 12 · 100.0% good

12

Steamboat Springs, CO

AQI 12 · 99.7% good

12

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Air Quality Guides

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Health Effects of Air Pollution

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Frequently Asked Questions

What is the air quality in the Evanston, WY metro area? ▼
The Evanston, WY metro area has a median Air Quality Index (AQI) of 7, rated "Good." 100.0% of monitored days (297 out of 297) had good air quality in 2024.
How many unhealthy air days does Evanston, WY have? ▼
In 2024, the Evanston, WY metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 44.
Is air quality in Evanston, WY getting better or worse? ▼
Air quality in the Evanston, WY metro is worsening based on 5-year trends (2020-2024). Best year: 2023 with 365 good days. Worst year: 2024 with 297 good days.
What does AQI 7 mean for health? ▼
An AQI of 7 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 Evanston, WY? ▼
The 90th percentile AQI for the Evanston, WY metro area is 17, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 44 (Good).
How does Evanston, WY compare to other metro areas? ▼
The Evanston, WY metro has 100.0% good air days. Similar metros: Pierre, SD (93.7% good), Mayaguez, PR (100.0% good), Ponce, PR (94.3% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset, 2020–2024. The AQS collects ambient air monitoring data from state, local, and tribal monitoring agencies across the United States.

Metrics: Air Quality Index (AQI) is calculated using EPA-standard breakpoints for six criteria pollutants: PM2.5, PM10, Ozone, NO2, CO, and SO2. Median AQI, max AQI, and 90th percentile AQI are computed from daily measurements. Good days percentage reflects days with AQI 0–50.

Coverage: 501 metro areas (Core Based Statistical Areas). Only metros with active monitoring stations are included. Unmonitored areas are not represented.

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

Source: U.S. EPA, AirNow / AQS Air Quality Index readings and pollutant concentrations · 2025