Median AQI
48
Good
South Dakota · County air quality · 2025
Brookings County, South Dakota
Median AQI 48 (Good). 53.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 48
- Median AQI
- 53.0%
- Good-air days
- 1
- Unhealthy days
- 8%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Brookings County's air is good on balance, among the most polluted counties nationally, a median AQI of 48 with 53.0% of 181 monitored days in the Good band, driven mainly by PM2.5.
- 48
- median AQI · Good
- 53.0%
- days rated Good
- PM2.5
- main pollutant
- 8%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 154.
Data updated July 2026
- Good · 96 d · 53.0%
- Moderate · 82 d · 45.3%
- USG · 2 d · 1.1%
- Unhealthy · 1 d · 0.6%
How did Brookings County's air break down in 2025?
Across 181 monitored days, 96 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 154 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 48 (Good).
Insights: Brookings County, South Dakota. EPA monitors recorded a median Air Quality Index of 48 across 181 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 96 (53%) fell in the Good band (AQI 0–50), 82 (45%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 73, while the worst single-day peak hit 154 (Unhealthy). Residents averaged about 15.9 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (136 days), Ozone (44 days), PM10 (1 days). Across the 2020–2025 trend window, good days shifted by -209 and the median AQI moved +9 points, placing the multi-year trajectory at worsening. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Brown (87.1% good, AQI 25); Clay (82.6% good, AQI 37); Codington (82.1% good, AQI 33); Custer (72.4% good, AQI 46); Hughes (94.4% good, AQI 14); Jackson (78.5% good, AQI 44).
Air Quality Summary
Good Days
53.0%
96 of 181 monitored days
-22.0pp vs 75% target
Max AQI Recorded
154
Unhealthy
Health Grade
Moderate
90th-pct AQI 73
Brookings County, Good days share 53.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Brookings County, Unhealthy-or-worse share 0.6%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 181 monitored days across EPA AQI categories.
Good
96
53%
Moderate
82
45%
USG
2
1%
Unhealthy
1
1%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Brookings County.
- PM2.5 · 136 days · 75.1%
- Ozone · 44 days · 24.3%
- PM10 · 1 days · 0.6%
Health Impact Assessment
Moderate
Brookings County's air quality is rated Moderate based on 53.0% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 2 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 154. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 136 of 181 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Brookings County. Best year: 2022 (320 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 305 | 61 | 0 | 0 | 39 | 87 |
| 2021 | 270 | 87 | 6 | 1 | 39 | 236 |
| 2022 | 320 | 44 | 0 | 0 | 36 | 87 |
| 2023 | 274 | 84 | 5 | 2 | 42 | 162 |
| 2024 | 292 | 72 | 2 | 0 | 36 | 111 |
| 2025 | 96 | 82 | 2 | 1 | 48 | 154 |
How does Brookings County compare?
How Brookings County compares
Good-day share worse than US avg
Brookings County 53.0%
Brown County, South Dakota 87.1%
US average 76.5%
Median AQI worse than US avg
Brookings County 48
Brown County, South Dakota 25
US average 38
Unhealthy days / yr worse than US avg
Brookings County 1
Brown County, South Dakota 0
US average 0
Other Counties in South Dakota
Air quality comparison for nearby counties in South Dakota.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Brookings County.
Black Hawk County, Iowa
AQI 48 · 56.6% good
Box Elder County, Utah
AQI 48 · 60.0% good
Clear Creek County, Colorado
AQI 48 · 64.4% good
Coconino County, Arizona
AQI 48 · 62.5% good
Columbia County, Florida
AQI 48 · 56.4% good
Davis County, Utah
AQI 48 · 59.5% good
What Brookings County's air means for you
On most days the air here is fine, but PM2.5 drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 48 means for exposure. Health guidance
- See how Brookings County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Brookings County with its South Dakota neighbours before drawing a conclusion about the region. All of South Dakota
Based on 181 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Brookings County, South Dakota? ▼
Brookings County has a median Air Quality Index (AQI) of 48, rated "Good." 53.0% of monitored days (96 out of 181) had good air quality in 2025.
What is the main pollutant in Brookings County? ▼
The primary pollutant in Brookings County is Fine Particles (PM2.5), which was the main AQI driver on 136 days (75% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Brookings County have? ▼
In 2025, Brookings County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 154.
Is the air quality in Brookings County getting better or worse? ▼
Air quality in Brookings County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 320 good days. Worst year: 2025 with 96 good days.
What does AQI 48 mean for health? ▼
Brookings County's median AQI of 48 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Brookings County compare to other counties in South Dakota? ▼
Brookings County has 53.0% good air days. Nearby counties in South Dakota: Brown (87.1% good), Clay (82.6% good), Codington (82.1% good), Custer (72.4% good), Hughes (94.4% good), Jackson (78.5% good).
What is the 90th percentile AQI in Brookings County? ▼
The 90th percentile AQI for Brookings County is 73, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 154 (Unhealthy).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
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.