San Diego Air Quality in Fall
Across 2019–2025, San Diego's fall (September–November) air quality had a median AQI of 71 (Moderate) over 637 monitored days in the San Diego-Carlsbad, CA area. 12.9% of fall days (82 of 637) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 57.8% of days. The cleanest fall on record here was 2025 (median AQI 58, 0 days above 100) and the worst was 2020 (median 93, 36 days above 100, peak AQI 192).
- Good: 9.4%
- Moderate: 77.7%
- Unhealthy for Sensitive Groups: 10.7%
- Unhealthy or worse: 2.2%
Extra Protection for San Diego Homes
Air quality in San Diego is moderate (AQI 54), 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.
Recommended: Coway AP-1512HH Mighty — True HEPA + carbon · CADR ~246 CFM · rooms up to 361 sq ft
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How is the air in San Diego in fall?
Moderate on a typical day: median AQI 71 across 2019–2025, with 12.9% of fall days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓9.4% of fall days were Good (AQI 0–50), 77.7% Moderate (51–100).
- ✓82 days of 637 reached AQI 101+; the fall peak was 192.
- ✓Cleanest month: November; worst month: September.
Frequently asked questions
What is the air quality like in San Diego in fall?▾
Across 2019–2025, the median daily AQI in San Diego in fall was 71 (Moderate). 9.4% of days were Good, 77.7% Moderate, and 12.9% reached Unhealthy for Sensitive Groups or worse, based on 637 monitored days in EPA's Air Quality System.
Is fall a good time for outdoor exercise in San Diego?▾
A typical fall day in San Diego is Moderate (median AQI 71): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 8 of fall days (12.9%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes San Diego's fall air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 57.8% of fall days in San Diego. The highest fall AQI recorded in 2019–2025 was 192 (Unhealthy), in 2020.
San Diego fall air quality, year by year
San Diego fall air quality by year (San Diego-Carlsbad, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 91 | 73 | 7 | 147 | PM2.5 |
| 2020worst | 91 | 93 | 36 | 192 | PM2.5 |
| 2021 | 91 | 64 | 4 | 133 | PM2.5 |
| 2022 | 91 | 64 | 6 | 145 | PM2.5 |
| 2023 | 91 | 67 | 10 | 133 | PM2.5 |
| 2024 | 91 | 77 | 19 | 161 | O3 |
| 2025cleanest | 91 | 58 | 0 | 97 | PM2.5 |
What fall air means in San Diego
A typical fall day in San Diego is Moderate (median AQI 71): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 8 of fall days (12.9%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Fall's median AQI of 71 is above San Diego's whole-year median of 67, making it one of the area's dirtier periods. Nationally, the median Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so San Diego runs above the national Fall norm; 12.9% of its Fall days topped AQI 100 versus 1.5% nationally (above average).
Within the season, November is the cleanest month (median AQI 69, 4.3% of days above 100) and September the worst (median 70, 17.6% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in San Diego
The latest EPA AirNow observation puts San Diego's AQI at 54 (PM2.5). The figures above are multi-year season statistics, not today's reading.
View current San Diego air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (San Diego-Carlsbad, 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.