Metro area air quality · 2025

Watertown, SD

Median AQI 33 (Good). 82.1% of monitored days rated Good across this metro's EPA monitoring network.

33
Median AQI
82.1%
Good-air days
1
Unhealthy days
69%
Cleaner than US metros

Aggregated from EPA Air Quality System (2025), 179 monitored days. EPA AQS →

The verdict

The Watertown, SD metro runs good on the EPA scale, cleaner than the median US metro, a median AQI of 33 with 82.1% of 179 monitored days in the Good band.

33
median AQI · Good
82.1%
days rated Good
69%
cleaner than US metros
154
worst single reading

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

Insights: Watertown, SD metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 33 over 179 measured days in 2025, which corresponds to a Good band and a Good metro-wide health grade. The monitored-day split lands at 147 Good days (82%), 30 Moderate (17%), and 1 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 57 while the highest single-day reading hit 154 (Unhealthy). Metro residents averaged roughly 24.6 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -146 and the median AQI moved -5 points, which classifies the multi-year trajectory as stable. The metro recorded 1 unhealthy-or-worse days combined, on those days the EPA recommends that sensitive groups limit prolonged outdoor exertion, and many schools and athletic programs adjust outdoor activity accordingly. Metros with comparable AQI profiles include Athens, OH (80.3% good, AQI 33); Crescent City, CA (81.0% good, AQI 33); Jackson, TN (79.6% good, AQI 33).

Air Quality Summary

Median AQI

33

Good

Good Days

82.1%

147 of 179 days

Max AQI

154

Unhealthy

Health Grade

Good

90th pct: 57

AQI Day Breakdown (2025)

Distribution of 179 monitored days across EPA AQI categories.

Good

147

82%

Moderate

30

17%

USG

1

1%

Unhealthy

1

1%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Watertown, SD metro area's air quality is rated Good based on 82.1% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.

Air quality is acceptable most days, but 1 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 154. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Watertown, SD metro compare?

How Watertown, SD compares

Good-day share better than US avg
Watertown, SD 82.1%
Athens, OH 80.3%
US average 71.3%
Median AQI better than US avg
Watertown, SD 33
Athens, OH 33
US average 41
Unhealthy days / yr about average
Watertown, SD 1
Athens, OH 0
US average 1

5-Year Air Quality Trend

Air quality is stable in the Watertown, SD metro. Best year: 2020 (293 good days).

Year Good Moderate Unhealthy Median AQI
2020 293 72 0 38
2021 246 113 2 43
2022 285 79 0 41
2023 215 135 1 45
2024 269 91 0 37
2025 147 30 1 33

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Watertown, SD.

Athens, OH

AQI 33 · 80.3% good

33

Crescent City, CA

AQI 33 · 81.0% good

33

Jackson, TN

AQI 33 · 79.6% good

33

Sheridan, WY

AQI 33 · 84.6% good

33

Bangor, ME

AQI 34 · 86.1% good

34

Baraboo, WI

AQI 34 · 79.6% good

34

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 Watertown, SD metro area? ▼
The Watertown, SD metro area has a median Air Quality Index (AQI) of 33, rated "Good." 82.1% of monitored days (147 out of 179) had good air quality in 2025.
How many unhealthy air days does Watertown, SD have? ▼
In 2025, the Watertown, SD metro area recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 154.
Is air quality in Watertown, SD getting better or worse? ▼
Air quality in the Watertown, SD metro is stable based on 5-year trends (2020-2025). Best year: 2020 with 293 good days. Worst year: 2025 with 147 good days.
What does AQI 33 mean for health? ▼
An AQI of 33 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 Watertown, SD? ▼
The 90th percentile AQI for the Watertown, SD metro area is 57, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 154 (Unhealthy).
How does Watertown, SD compare to other metro areas? ▼
The Watertown, SD metro has 82.1% good air days. Similar metros: Athens, OH (80.3% good), Crescent City, CA (81.0% good), Jackson, TN (79.6% 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.