Indianapolis Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Indianapolis (Indianapolis-Carmel-Anderson, IN area) was June 28, 2023, when the daily AQI reached 259 (Very Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 7 of the 10 worst days were Unhealthy (AQI 151+) or worse; 9 of the 10 were driven by fine particulate matter (PM2.5) and 1 by ground-level ozone, and 5 of them fell in 2023. The cleanest day was November 21, 2024 at AQI 23 (Good); the 10 best days span 6 different years.
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Air quality in Indianapolis is moderate (AQI 55), with fine particles (PM2.5) the main concern. A True-HEPA purifier gives sensitive groups — kids, seniors and anyone with asthma or allergies — cleaner air indoors on days like today.
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When were Indianapolis's worst and best air quality days?
Worst: June 28, 2023, AQI 259 (Very Unhealthy, PM2.5). Best: November 21, 2024, AQI 23 (Good). Based on 2,557 EPA-monitored days in the Indianapolis-Carmel-Anderson, IN area, 2019–2025.
- ✓7 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 138 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) drove 9 of the 10 worst days.
- ✓2023 accounts for 5 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Indianapolis?▾
June 28, 2023: the Indianapolis-Carmel-Anderson, IN area's daily AQI hit 259 (Very Unhealthy), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in Indianapolis?▾
November 21, 2024, with a daily AQI of 23 (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 Indianapolis's worst air quality day in 2025?▾
July 5, 2025, AQI 170 (Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season.
Which pollutant causes Indianapolis's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 9 of the 10 worst days; ground-level ozone on 1. The tables above list the defining pollutant for every day.
Indianapolis's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Indianapolis-Carmel-Anderson, IN area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 259 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 229 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2023 page) | 181 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2025 page) | 170 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2025 page) | 154 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 6 | (2022 page) | 154 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2023 page) | 151 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 8 | (2020 page) | 144 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2024 page) | 138 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 10 | (2023 page) | 138 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
Worst day of each year in Indianapolis
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 | 119 | Unhealthy for Sensitive Groups | O3 — ground-level ozone | |
| 2020 | 144 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) | |
| 2021 | 114 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) | |
| 2022 | 154 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2023 | 259 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 138 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2025 | 170 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Indianapolis's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Indianapolis-Carmel-Anderson, IN area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2024 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2023 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2023 page) | 23 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2019 page) | 23 | Good | O3 — ground-level ozone |
| 5 | (2025 page) | 25 | Good | O3 — ground-level ozone |
| 6 | (2025 page) | 25 | Good | O3 — ground-level ozone |
| 7 | (2022 page) | 25 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2021 page) | 25 | Good | NO2 — nitrogen dioxide |
| 9 | (2025 page) | 26 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2025 page) | 26 | Good | O3 — ground-level ozone |
Right now in Indianapolis
The latest EPA AirNow observation puts Indianapolis's AQI at 55 (PM2.5). The days above are historical records, not today's reading.
View current Indianapolis air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Indianapolis-Carmel-Anderson, IN), 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.