San Diego Air Quality in January
Across 2019–2025, San Diego's January air quality had a median AQI of 63 (Moderate) over 217 monitored days in the San Diego-Carlsbad, CA area. 2.3% of January days (5 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 88.5% of days. The cleanest January on record here was 2022 (median AQI 59, 0 days above 100) and the worst was 2025 (median 72, 3 days above 100, peak AQI 154).
- Good: 11.5%
- Moderate: 86.2%
- Unhealthy for Sensitive Groups: 1.8%
- Unhealthy or worse: 0.5%
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 January?
Moderate on a typical day: median AQI 63 across 2019–2025, with 2.3% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓11.5% of January days were Good (AQI 0–50), 86.2% Moderate (51–100).
- ✓5 days of 217 reached AQI 101+; the January peak was 154.
- ✓Best January: 2022; worst January: 2025.
Frequently asked questions
What is the air quality like in San Diego in January?▾
Across 2019–2025, the median daily AQI in San Diego in January was 63 (Moderate). 11.5% of days were Good, 86.2% Moderate, and 2.3% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is January a good time for outdoor exercise in San Diego?▾
A typical January day in San Diego is Moderate (median AQI 63): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 43 of January days (2.3%) 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 January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 88.5% of January days in San Diego. The highest January AQI recorded in 2019–2025 was 154 (Unhealthy), in 2025.
San Diego January air quality, year by year
San Diego January 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 | 31 | 58 | 1 | 101 | PM2.5 |
| 2020 | 31 | 66 | 0 | 90 | PM2.5 |
| 2021 | 31 | 77 | 0 | 93 | PM2.5 |
| 2022cleanest | 31 | 59 | 0 | 85 | PM2.5 |
| 2023 | 31 | 56 | 1 | 111 | PM2.5 |
| 2024 | 31 | 63 | 0 | 90 | PM2.5 |
| 2025worst | 31 | 72 | 3 | 154 | PM2.5 |
What January air means in San Diego
A typical January day in San Diego is Moderate (median AQI 63): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 43 of January days (2.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
January's median AQI of 63 is below San Diego's whole-year median of 67, making it one of the area's cleaner periods. Nationally, the median January AQI across every EPA metro area (95,602 metro-days, 2019–2025) is 39, so San Diego runs above the national January norm; 2.3% of its January days topped AQI 100 versus 0.7% nationally (above average).
January is part of San Diego's winter season (December, January, February); the winter page pools all three months.
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 month 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.