Metro area air quality · 2025

Eureka-Arcata-Fortuna, CA

Median AQI 36 (Good). 83.2% of monitored days rated Good across this metro's EPA monitoring network.

36
Median AQI
83.2%
Good-air days
0
Unhealthy days
72%
Cleaner than US metros

Aggregated from EPA Air Quality System (2025), 303 monitored days. EPA AQS →

The verdict

The Eureka-Arcata-Fortuna, CA metro runs good on the EPA scale, cleaner than the median US metro, a median AQI of 36 with 83.2% of 303 monitored days in the Good band.

36
median AQI · Good
83.2%
days rated Good
72%
cleaner than US metros
75
worst single reading

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

Insights: Eureka-Arcata-Fortuna, CA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 36 over 303 measured days in 2025, which corresponds to a Good band and a Good metro-wide health grade. The monitored-day split lands at 252 Good days (83%), 51 Moderate (17%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 54 while the highest single-day reading hit 75 (Moderate). Metro residents averaged roughly 25.0 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -66 and the median AQI moved +7 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 Augusta-Waterville, ME (83.5% good, AQI 36); Beatrice, NE (74.0% good, AQI 36); Iowa City, IA (71.0% good, AQI 36).

Air Quality Summary

Median AQI

36

Good

Good Days

83.2%

252 of 303 days

Max AQI

75

Moderate

Health Grade

Good

90th pct: 54

AQI Day Breakdown (2025)

Distribution of 303 monitored days across EPA AQI categories.

Good

252

83%

Moderate

51

17%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Eureka-Arcata-Fortuna, CA metro area's air quality is rated Good based on 83.2% 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 Eureka-Arcata-Fortuna, CA metro compare?

How Eureka-Arcata-Fortuna, CA compares

Good-day share better than US avg
Eureka-Arcata-Fortuna, CA 83.2%
Augusta-Waterville, ME 83.5%
US average 71.3%
Median AQI better than US avg
Eureka-Arcata-Fortuna, CA 36
Augusta-Waterville, ME 36
US average 41
Unhealthy days / yr better than US avg
Eureka-Arcata-Fortuna, CA 0
Augusta-Waterville, ME 0
US average 1

5-Year Air Quality Trend

Air quality is worsening in the Eureka-Arcata-Fortuna, CA metro. Best year: 2022 (340 good days).

Year Good Moderate Unhealthy Median AQI
2020 318 44 1 29
2021 333 32 0 29
2022 340 25 0 24
2023 284 70 1 32
2024 266 100 0 38
2025 252 51 0 36

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Eureka-Arcata-Fortuna, CA.

Augusta-Waterville, ME

AQI 36 · 83.5% good

36

Beatrice, NE

AQI 36 · 74.0% good

36

Iowa City, IA

AQI 36 · 71.0% good

36

Kennewick-Richland, WA

AQI 36 · 86.0% good

36

Lincoln, NE

AQI 36 · 77.7% good

36

Longview, TX

AQI 36 · 88.9% good

36

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 Eureka-Arcata-Fortuna, CA metro area? ▼
The Eureka-Arcata-Fortuna, CA metro area has a median Air Quality Index (AQI) of 36, rated "Good." 83.2% of monitored days (252 out of 303) had good air quality in 2025.
How many unhealthy air days does Eureka-Arcata-Fortuna, CA have? ▼
In 2025, the Eureka-Arcata-Fortuna, CA metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 75.
Is air quality in Eureka-Arcata-Fortuna, CA getting better or worse? ▼
Air quality in the Eureka-Arcata-Fortuna, CA metro is worsening based on 5-year trends (2020-2025). Best year: 2022 with 340 good days. Worst year: 2025 with 252 good days.
What does AQI 36 mean for health? ▼
An AQI of 36 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 Eureka-Arcata-Fortuna, CA? ▼
The 90th percentile AQI for the Eureka-Arcata-Fortuna, CA metro area is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 75 (Moderate).
How does Eureka-Arcata-Fortuna, CA compare to other metro areas? ▼
The Eureka-Arcata-Fortuna, CA metro has 83.2% good air days. Similar metros: Augusta-Waterville, ME (83.5% good), Beatrice, NE (74.0% good), Iowa City, IA (71.0% 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.