Metro area air quality · 2024

Shelton, WA

Median AQI 21 (Good). 93.2% of monitored days rated Good across this metro's EPA monitoring network.

21
Median AQI
93.2%
Good-air days
0
Unhealthy days
90%
Cleaner than US metros

Aggregated from EPA Air Quality System (2024), 366 monitored days. EPA AQS → · NOAA →

Insights: Shelton, WA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 21 over 366 measured days in 2024, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 341 Good days (93%), 25 Moderate (7%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 43 while the highest single-day reading hit 73 (Moderate). Metro residents averaged roughly 28.0 clean-air days per 30-day window across the reporting year.

Across the 2020–2024 trend window, good days shifted by +29 and the median AQI moved -2 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 Hilo, HI (97.0% good, AQI 21); Kahului-Wailuku-Lahaina, HI (99.7% good, AQI 21); Aberdeen, WA (96.5% good, AQI 20).

Air Quality Summary

Median AQI

21

Good

Good Days

93.2%

341 of 366 days

Max AQI

73

Moderate

Health Grade

Excellent

90th pct: 43

AQI Day Breakdown (2024)

Distribution of 366 monitored days across EPA AQI categories.

Good

341

93%

Moderate

25

7%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Excellent

The Shelton, WA metro area's air quality is rated Excellent based on 93.2% 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 Shelton, WA metro compare?

How Shelton, WA compares

Good-day share better than US avg
Shelton, WA 93.2%
Hilo, HI 97.0%
US average 70.2%
Median AQI better than US avg
Shelton, WA 21
Hilo, HI 21
US average 41
Unhealthy days / yr better than US avg
Shelton, WA 0
Hilo, HI 0
US average 1

5-Year Air Quality Trend

Air quality is improving in the Shelton, WA metro. Best year: 2024 (341 good days).

Year Good Moderate Unhealthy Median AQI
2020 312 36 2 23
2021 339 22 0 22
2022 302 60 0 23
2023 313 49 0 24
2024 341 25 0 21

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Shelton, WA.

Hilo, HI

AQI 21 · 97.0% good

21

Kahului-Wailuku-Lahaina, HI

AQI 21 · 99.7% good

21

Aberdeen, WA

AQI 20 · 96.5% good

20

Centralia, WA

AQI 22 · 93.3% good

22

Gardnerville Ranchos, NV

AQI 22 · 90.1% good

22

Longview, WA

AQI 22 · 95.4% good

22

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Frequently Asked Questions

What is the air quality in the Shelton, WA metro area? ▼
The Shelton, WA metro area has a median Air Quality Index (AQI) of 21, rated "Good." 93.2% of monitored days (341 out of 366) had good air quality in 2024.
How many unhealthy air days does Shelton, WA have? ▼
In 2024, the Shelton, WA metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 73.
Is air quality in Shelton, WA getting better or worse? ▼
Air quality in the Shelton, WA metro is improving based on 5-year trends (2020-2024). Best year: 2024 with 341 good days. Worst year: 2022 with 302 good days.
What does AQI 21 mean for health? ▼
An AQI of 21 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 Shelton, WA? ▼
The 90th percentile AQI for the Shelton, WA metro area is 43, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 73 (Moderate).
How does Shelton, WA compare to other metro areas? ▼
The Shelton, WA metro has 93.2% good air days. Similar metros: Hilo, HI (97.0% good), Kahului-Wailuku-Lahaina, HI (99.7% good), Aberdeen, WA (96.5% 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