Sioux Falls Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Sioux Falls (Sioux Falls, SD area) was July 30, 2021, when the daily AQI reached 193 (Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,539 monitored days in 2019–2025, 6 of the 10 worst days were Unhealthy (AQI 151+) or worse; 6 of the 10 were driven by fine particulate matter (PM2.5) and 3 by ground-level ozone, and 7 of them fell in 2023. The cleanest day was July 2, 2024 at AQI 5 (Good); the 10 best days span 3 different years.
Reduce Indoor Ozone in Sioux Falls
Today's main pollutant in Sioux Falls is ground-level ozone (AQI 24). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
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When were Sioux Falls's worst and best air quality days?
Worst: July 30, 2021, AQI 193 (Unhealthy, PM2.5). Best: July 2, 2024, AQI 5 (Good). Based on 2,539 EPA-monitored days in the Sioux Falls, SD area, 2019–2025.
- ✓6 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 142 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) drove 6 of the 10 worst days.
- ✓2023 accounts for 7 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Sioux Falls?▾
July 30, 2021: the Sioux Falls, SD area's daily AQI hit 193 (Unhealthy), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,539 monitored days in 2019–2025.
What was the best air quality day in Sioux Falls?▾
July 2, 2024, with a daily AQI of 5 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was Sioux Falls's worst air quality day in 2025?▾
August 1, 2025, AQI 125 (Unhealthy for Sensitive Groups), set by fine particulate matter (PM2.5), in wildfire smoke season.
Which pollutant causes Sioux Falls's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 6 of the 10 worst days; ground-level ozone on 3. The tables above list the defining pollutant for every day.
Sioux Falls's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Sioux Falls, SD area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2021 page) | 193 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 181 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2021 page) | 172 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2023 page) | 157 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2023 page) | 157 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 6 | (2023 page) | 154 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 7 | (2023 page) | 147 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 8 | (2024 page) | 145 | Unhealthy for Sensitive Groups | PM10 — coarse dust (PM10) |
| 9 | (2023 page) | 143 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 10 | (2023 page) | 142 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Worst day of each year in Sioux Falls
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 105 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 90 | Moderate | O3 — ground-level ozone, in peak ozone season | |
| 2021 | 193 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2022 | 105 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 181 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2024 | 145 | Unhealthy for Sensitive Groups | PM10 — coarse dust (PM10) | |
| 2025 | 125 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Sioux Falls's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Sioux Falls, SD area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2024 page) | 5 | Good | NO2 — nitrogen dioxide |
| 2 | (2019 page) | 5 | Good | NO2 — nitrogen dioxide |
| 3 | (2024 page) | 6 | Good | NO2 — nitrogen dioxide |
| 4 | (2024 page) | 6 | Good | NO2 — nitrogen dioxide |
| 5 | (2019 page) | 6 | Good | PM10 — coarse dust (PM10) |
| 6 | (2024 page) | 7 | Good | NO2 — nitrogen dioxide |
| 7 | (2021 page) | 7 | Good | PM10 — coarse dust (PM10) |
| 8 | (2024 page) | 8 | Good | PM10 — coarse dust (PM10) |
| 9 | (2021 page) | 8 | Good | NO2 — nitrogen dioxide |
| 10 | (2021 page) | 8 | Good | PM10 — coarse dust (PM10) |
Right now in Sioux Falls
The latest EPA AirNow observation puts Sioux Falls's AQI at 24 (O3). The days above are historical records, not today's reading.
View current Sioux Falls air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Sioux Falls, SD), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.