Metro area air quality · 2025

Sonora, CA

Median AQI 40 (Good). 83.3% of monitored days rated Good across this metro's EPA monitoring network.

40
Median AQI
83.3%
Good-air days
0
Unhealthy days
72%
Cleaner than US metros

Aggregated from EPA Air Quality System (2025), 210 monitored days. EPA AQS →

The verdict

The Sonora, CA metro runs good on the EPA scale, cleaner than the median US metro, a median AQI of 40 with 83.3% of 210 monitored days in the Good band.

40
median AQI · Good
83.3%
days rated Good
72%
cleaner than US metros
87
worst single reading

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

Insights: Sonora, CA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 40 over 210 measured days in 2025, which corresponds to a Good band and a Good metro-wide health grade. The monitored-day split lands at 175 Good days (83%), 35 Moderate (17%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 58 while the highest single-day reading hit 87 (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 -102 and the median AQI moved -1 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 Berlin, NH-VT (85.4% good, AQI 40); Burlington-South Burlington, VT (91.2% good, AQI 40); Cambridge, MD (84.4% good, AQI 40).

Air Quality Summary

Median AQI

40

Good

Good Days

83.3%

175 of 210 days

Max AQI

87

Moderate

Health Grade

Good

90th pct: 58

AQI Day Breakdown (2025)

Distribution of 210 monitored days across EPA AQI categories.

Good

175

83%

Moderate

35

17%

USG

0

0%

Unhealthy

0

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Sonora, CA metro area's air quality is rated Good based on 83.3% 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 Sonora, CA metro compare?

How Sonora, CA compares

Good-day share better than US avg
Sonora, CA 83.3%
Berlin, NH-VT 85.4%
US average 71.3%
Median AQI better than US avg
Sonora, CA 40
Berlin, NH-VT 40
US average 41
Unhealthy days / yr better than US avg
Sonora, CA 0
Berlin, NH-VT 0
US average 1

5-Year Air Quality Trend

Air quality is improving in the Sonora, CA metro. Best year: 2021 (295 good days).

Year Good Moderate Unhealthy Median AQI
2020 277 71 0 41
2021 295 63 0 41
2022 237 12 0 39
2023 237 51 0 43
2024 286 64 0 40
2025 175 35 0 40

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Sonora, CA.

Berlin, NH-VT

AQI 40 · 85.4% good

40

Burlington-South Burlington, VT

AQI 40 · 91.2% good

40

Cambridge, MD

AQI 40 · 84.4% good

40

Charleston, WV

AQI 40 · 79.6% good

40

Corning, NY

AQI 40 · 80.2% good

40

Dickinson, ND

AQI 40 · 80.3% good

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 Sonora, CA metro area? ▼
The Sonora, CA metro area has a median Air Quality Index (AQI) of 40, rated "Good." 83.3% of monitored days (175 out of 210) had good air quality in 2025.
How many unhealthy air days does Sonora, CA have? ▼
In 2025, the Sonora, CA metro area recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 87.
Is air quality in Sonora, CA getting better or worse? ▼
Air quality in the Sonora, CA metro is improving based on 5-year trends (2020-2025). Best year: 2021 with 295 good days. Worst year: 2025 with 175 good days.
What does AQI 40 mean for health? ▼
An AQI of 40 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 Sonora, CA? ▼
The 90th percentile AQI for the Sonora, CA metro area is 58, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 87 (Moderate).
How does Sonora, CA compare to other metro areas? ▼
The Sonora, CA metro has 83.3% good air days. Similar metros: Berlin, NH-VT (85.4% good), Burlington-South Burlington, VT (91.2% good), Cambridge, MD (84.4% 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.