Fresno Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Fresno (Fresno, CA area) was September 13, 2020, when the daily AQI reached 346 (Hazardous), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 10 of the 10 worst days were Unhealthy (AQI 151+) or worse; 8 of the 10 were driven by fine particulate matter (PM2.5) and 2 by coarse dust (PM10), and 8 of them fell in 2020. The cleanest day was October 27, 2025 at AQI 25 (Good); the 10 best days span 3 different years.
Extra Protection for Fresno Homes
Air quality in Fresno is moderate (AQI 69), with particle pollution 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 Fresno's worst and best air quality days?
Worst: September 13, 2020, AQI 346 (Hazardous, PM2.5). Best: October 27, 2025, AQI 25 (Good). Based on 2,557 EPA-monitored days in the Fresno, CA area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 207 (Very Unhealthy).
- ✓Fine particulate matter (PM2.5) drove 8 of the 10 worst days.
- ✓2020 accounts for 8 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Fresno?▾
September 13, 2020: the Fresno, CA area's daily AQI hit 346 (Hazardous), 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 Fresno?▾
October 27, 2025, with a daily AQI of 25 (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 Fresno's worst air quality day in 2025?▾
May 31, 2025, AQI 164 (Unhealthy), set by ground-level ozone.
Which pollutant causes Fresno's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 8 of the 10 worst days; coarse dust (PM10) on 2. The tables above list the defining pollutant for every day.
Fresno's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Fresno, CA area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2020 page) | 346 | Hazardous | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2020 page) | 290 | Very Unhealthy | PM10 — coarse dust (PM10) |
| 3 | (2021 page) | 278 | Very Unhealthy | PM10 — coarse dust (PM10) |
| 4 | (2020 page) | 274 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2020 page) | 259 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 6 | (2020 page) | 254 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 7 | (2020 page) | 243 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 8 | (2020 page) | 224 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 9 | (2021 page) | 223 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 10 | (2020 page) | 207 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
Worst day of each year in Fresno
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 | 187 | Unhealthy | PM10 — coarse dust (PM10) | |
| 2020 | 346 | Hazardous | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2021 | 278 | Very Unhealthy | PM10 — coarse dust (PM10) | |
| 2022 | 159 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 156 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2024 | 169 | Unhealthy | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 164 | Unhealthy | O3 — ground-level ozone |
Fresno's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Fresno, CA area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2025 page) | 25 | Good | O3 — ground-level ozone |
| 2 | (2023 page) | 29 | Good | O3 — ground-level ozone |
| 3 | (2023 page) | 29 | Good | O3 — ground-level ozone |
| 4 | (2022 page) | 29 | Good | O3 — ground-level ozone |
| 5 | (2022 page) | 29 | Good | O3 — ground-level ozone |
| 6 | (2023 page) | 31 | Good | O3 — ground-level ozone |
| 7 | (2023 page) | 31 | Good | O3 — ground-level ozone |
| 8 | (2023 page) | 31 | Good | O3 — ground-level ozone |
| 9 | (2022 page) | 31 | Good | O3 — ground-level ozone |
| 10 | (2022 page) | 31 | Good | O3 — ground-level ozone |
Right now in Fresno
The latest EPA AirNow observation puts Fresno's AQI at 69 (PM10). The days above are historical records, not today's reading.
View current Fresno air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Fresno, CA), 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.