Metro area air quality · 2025

Bellingham, WA

Median AQI 31 (Good). 94.0% of monitored days rated Good across this metro's EPA monitoring network.

Compiled by PlainAirData · August 23, 2026

31
Median AQI: 94.0%
Good-air days: 1
Unhealthy days: 93%
Cleaner than US metros

Bellingham, WA posted a 2025 median AQI of 31 (Good) with 94.0% Good days

According to the U.S. EPA Air Quality System, the Bellingham, WA CBSA recorded a median AQI of 31 across 364 monitored days in 2025, with 94.0% rated Good and 1 unhealthy or worse. This is an annual metro comparison, not a live advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US metros: The Bellingham, WA CBSA's 94.0% Good-day share places it cleaner than 93% of US metros in 2025.
Closest median-AQI peer: Athens, OH (83.4% Good, median AQI 31) is the closest nationwide median-AQI peer to Bellingham, WA.
2020–2025 Good-day shift: Bellingham, WA's Good-day share moved -0.5 points from 2020 to 2025 (median AQI +7).
Median AQI: Median AQI: 31

Aggregated from EPA Air Quality System (2025), 364 monitored days. EPA AQS →

The verdict

The Bellingham, WA metro runs good on the EPA scale, among the cleanest 10% of US metros, a median AQI of 31 with 94.0% of 364 monitored days in the Good band.

31
median AQI · Good: 94.0%
days rated Good: 93%
cleaner than US metros: 152
worst single reading

1 day reached Unhealthy or worse across the metro's monitors in 2025.

Bellingham, WA metro's peak single-day AQI rose from 82 to 152 between the 2024 and 2025 EPA annual releases, a change of +70 points.
Bellingham, WA metro's Good-day share rose from 92.8% to 94.0% between the 2024 and 2025 EPA annual releases, a change of +1.2 percentage points.
Bellingham, WA metro's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.

Insights: Bellingham, WA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 31 over 364 measured days in 2025, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 342 Good days (94%), 21 Moderate (6%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 46 while the highest single-day reading hit 152 (Unhealthy). Metro residents averaged roughly 28.2 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -0.5 points and the median AQI moved +7 points, which classifies the multi-year trajectory as worsening. The annual record contains 1 day at Unhealthy or worse. On that day, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Metros with comparable AQI profiles include Athens, OH (83.4% good, AQI 31); Clearlake, CA (99.2% good, AQI 31); Coeur d'Alene, ID (77.8% good, AQI 31).

Air Quality Summary

Median AQI

Good

Good Days

94.0%

342 of 364 days

Max AQI

152

Unhealthy

Health Grade

Excellent

90th pct: 46

AQI Day Breakdown (2025)

Distribution of 364 monitored days across EPA AQI categories.

Good

342

94%

Moderate

USG

Unhealthy

Very Unhealthy

Hazardous

Health Impact Assessment

Excellent

The Bellingham, WA metro area's air quality is rated Excellent based on 94.0% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.

Air quality is acceptable most days, but 0 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 152. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Bellingham, WA metro compare?

How Bellingham, WA compares

Compare against

Good-day share better than typical

Bellingham, WA 94.0%

Athens, OH 83.4%

Typical US metro 70.6%

Median AQI better than typical

Bellingham, WA 31

Athens, OH 31

Typical US metro 41

Unhealthy days / yr about typical

Bellingham, WA 1

Athens, OH 0

Typical US metro 1

5-Year Air Quality Trend

Air quality is worsening in the Bellingham, WA metro. Highest Good-day share: 2021 (97.9%, 323 of 330 monitored days).

Year	Good	Moderate	Unhealthy	Median AQI	Max AQI
2020	341	16	4	24	237
2021	323	7	0	28	129
2022	294	40	5	32	243
2023	327	33	0	31	94
2024	335	26	0	33	82
2025	342	21	1	31	152

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Bellingham, WA (31).

Athens, OH

Median AQI 31 · 83.4% Good-day share

Clearlake, CA

Median AQI 31 · 99.2% Good-day share

Coeur d'Alene, ID

Median AQI 31 · 77.8% Good-day share

Moscow, ID

Median AQI 31 · 83.4% Good-day share

Cookeville, TN

Median AQI 30 · 90.0% Good-day share

Crescent City, CA

Median AQI 32 · 81.8% Good-day share

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Bellingham, WA's 1 (independent of median AQI).

Ann Arbor, MI

1 unhealthy-or-worse days · median AQI 41

Bangor, ME

1 unhealthy-or-worse days · median AQI 33

Baraboo, WI

1 unhealthy-or-worse days · median AQI 35

Bartlesville, OK

1 unhealthy-or-worse days · median AQI 44

Beaumont-Port Arthur, TX

1 unhealthy-or-worse days · median AQI 52

Beaver Dam, WI

1 unhealthy-or-worse days · median AQI 40

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 Bellingham, WA metro area? ▼

The Bellingham, WA metro area has a median Air Quality Index (AQI) of 31, rated "Good." 94.0% of monitored days (342 out of 364) had good air quality in 2025.

How many unhealthy air days does Bellingham, WA have? ▼

In 2025, the Bellingham, WA metro area recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 152.

Is air quality in Bellingham, WA getting better or worse? ▼

Air quality in the Bellingham, WA metro 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: 2021 at 97.9% (323 of 330 days). Lowest qualifying Good-day share: 2022 at 86.7% (294 of 339 days).

What does AQI 31 mean for health? ▼

An AQI of 31 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 Bellingham, WA? ▼

The 90th percentile AQI for the Bellingham, WA metro area is 46, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 152 (Unhealthy).

How does Bellingham, WA compare to other metro areas? ▼

The Bellingham, WA metro has 94.0% good air days. Similar metros: Athens, OH (83.4% good), Clearlake, CA (99.2% good), Coeur d'Alene, ID (77.8% 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 Accessed 2026-07-06

Send the source-year summary or download its ready-to-use data card.

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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.