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.

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

Bellingham, WA sits in the upper Good-day tercile among EPA CBSA metros on this site (94.0% of 364 monitored days). On the EPA scale the metro runs good, among the cleanest 10% of US metros, with a median AQI of 31 and 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.

Annual release change

What changed in the 2025 EPA annual release

2024 → 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.

Compared against 361 monitored days in 2024 and 364 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Bellingham, WA sits in the upper Good-day tercile among EPA CBSA metros on this site (94.0% of 364 monitored days). Signature read: 94.0% Good-day share (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 31 over 364 measured days in 2025 (Good / Excellent). The monitored-day split lands at 342 Good (94%), 21 Moderate (6%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 46; the highest single-day reading hit 152 (Unhealthy).

Across 2020–2025, Good-day share shifted -0.5 points and median AQI moved +7 (worsening). The annual record contains 1 day at Unhealthy or worse. 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).

Health effects of air pollution →

Air Quality Summary

Median AQI

31

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

21

6%

USG

0

0%

Unhealthy

1

0%

Very Unhealthy

0

0%

Hazardous

0

0%

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

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
2020 341 16 4 24
2021 323 7 0 28
2022 294 40 5 32
2023 327 33 0 31
2024 335 26 0 33
2025 342 21 1 31

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

31

Clearlake, CA

Median AQI 31 · 99.2% Good-day share

31

Coeur d'Alene, ID

Median AQI 31 · 77.8% Good-day share

31

Moscow, ID

Median AQI 31 · 83.4% Good-day share

31

Cookeville, TN

Median AQI 30 · 90.0% Good-day share

30

Crescent City, CA

Median AQI 32 · 81.8% Good-day share

32

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

41

Bangor, ME

1 unhealthy-or-worse days · median AQI 33

33

Baraboo, WI

1 unhealthy-or-worse days · median AQI 35

35

Bartlesville, OK

1 unhealthy-or-worse days · median AQI 44

44

Beaumont-Port Arthur, TX

1 unhealthy-or-worse days · median AQI 52

52

Beaver Dam, WI

1 unhealthy-or-worse days · median AQI 40

40

Frequently Asked Questions

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.
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.
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.
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).
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).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Bellingham, WA, 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, Bellingham, WA · 2020–2025