Los Angeles Air Quality in Winter
Across 2019–2025, Los Angeles's winter (December–February) air quality had a median AQI of 67 (Moderate) over 632 monitored days in the Los Angeles-Long Beach-Anaheim, CA area. 8.3% of winter days (53 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 89.1% of days. The cleanest winter on record here was 2019 (median AQI 63, 2 days above 100) and the worst was 2025 (median 70, 16 days above 100, peak AQI 182).
- Good: 7.9%
- Moderate: 83.7%
- Unhealthy for Sensitive Groups: 6.6%
- Unhealthy or worse: 1.7%
Reduce Indoor Ozone in Los Angeles
Today's main pollutant in Los Angeles is ground-level ozone (AQI 38). 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.
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How is the air in Los Angeles in winter?
Moderate on a typical day: median AQI 67 across 2019–2025, with 8.3% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓7.9% of winter days were Good (AQI 0–50), 83.7% Moderate (51–100).
- ✓53 days of 632 reached AQI 101+; the winter peak was 184.
- ✓Cleanest month: February; worst month: December.
Frequently asked questions
What is the air quality like in Los Angeles in winter?▾
Across 2019–2025, the median daily AQI in Los Angeles in winter was 67 (Moderate). 7.9% of days were Good, 83.7% Moderate, and 8.3% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Los Angeles?▾
A typical winter day in Los Angeles is Moderate (median AQI 67): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 12 of winter days (8.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Los Angeles's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 89.1% of winter days in Los Angeles. The highest winter AQI recorded in 2019–2025 was 184 (Unhealthy), in 2025.
Los Angeles winter air quality, year by year
Los Angeles winter air quality by year (Los Angeles-Long Beach-Anaheim, CA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 90 | 63 | 2 | 125 | PM2.5 |
| 2020 | 91 | 74 | 10 | 130 | PM2.5 |
| 2021 | 90 | 69 | 8 | 184 | PM2.5 |
| 2022 | 90 | 69 | 5 | 148 | PM2.5 |
| 2023 | 90 | 65 | 2 | 153 | PM2.5 |
| 2024 | 91 | 67 | 10 | 155 | PM2.5 |
| 2025worst | 90 | 70 | 16 | 182 | PM2.5 |
What winter air means in Los Angeles
A typical winter day in Los Angeles is Moderate (median AQI 67): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 12 of winter days (8.3%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Winter's median AQI of 67 is below Los Angeles's whole-year median of 74, making it one of the area's cleaner periods. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Los Angeles runs above the national Winter norm; 8.3% of its Winter days topped AQI 100 versus 0.6% nationally (above average).
Within the season, February is the cleanest month (median AQI 62, 0.5% of days above 100) and December the worst (median 74, 16.2% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Los Angeles
The latest EPA AirNow observation puts Los Angeles's AQI at 38 (O3). The figures above are multi-year season statistics, not today's reading.
View current Los Angeles air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Los Angeles-Long Beach-Anaheim, 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.