California · County air quality · 2025

Los Angeles County, California

Median AQI 74 (Moderate). 10.7% of monitored days rated Good, direct from EPA Air Quality System stations.

74
Median AQI
10.7%
Good-air days
32
Unhealthy days
0%
Cleaner than US counties

Los Angeles County's 2025 annual median AQI is 74 (Moderate), with 10.7% Good days

According to the U.S. EPA Air Quality System, Los Angeles County, California posted a 2025 median AQI of 74 (Moderate) across 365 monitored days, with 10.7% rated Good and 32 unhealthy or worse. This is an annual comparison, not today's advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US
Los Angeles County's 10.7% Good-day share places it cleaner than 0% of US counties in 2025.
Closest median-AQI peer
Maricopa County (8.8% Good, median AQI 73) is the closest nationwide median-AQI peer to Los Angeles County.
2020–2025 trend
Los Angeles County's floor-qualifying Good-day share is improving from 2020 to 2025 (10.0% → 10.7%).
Median AQI
Median AQI: 74

According to the 2025 EPA AQS county release on PlainAirData, Los Angeles County, California ranks #949 of 951 by median AQI (74) and #949 by good-day share (10.7%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Los Angeles County's Unhealthy-category days fell from 46 to 31 between the 2024 and 2025 EPA annual releases, a change of -15 days.
  • Los Angeles County's peak single-day AQI fell from 230 to 201 between the 2024 and 2025 EPA annual releases, a change of -29 points.
  • Los Angeles County's median AQI fell from 80 to 74 between the 2024 and 2025 EPA annual releases, a change of -6 points.

Compared against 366 monitored days in 2024 and 365 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Data updated August 2026

Los Angeles County AQI category distribution Stacked-segment bar showing the share of monitored days that fell in each EPA AQI category, Good, Moderate, USG, Unhealthy, Very Unhealthy, Hazardous, with median AQI marker. AQI category distribution 365 monitored days G M U Median AQI 74 0 50 100 150 200 300 500 Los Angeles County
  • Good · 39 d · 10.7%
  • Moderate · 228 d · 62.5%
  • USG · 66 d · 18.1%
  • Unhealthy · 31 d · 8.5%
  • Very Unhealthy · 1 d · 0.3%

How did Los Angeles County's air break down in 2025?

Across 365 monitored days, 39 fell in the Good band (AQI 0–50) and 32 reached Unhealthy or worse. The worst single day peaked at AQI 201 (Very Unhealthy).

EPA AQS →
Los Angeles County, Good days share 10.7%
National avg

Share of monitored days at AQI 0-50 (Good band).

Los Angeles County, Unhealthy-or-worse share 87.7%
National avg

Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).

Where Los Angeles County sits nationally

COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Los Angeles County's Good-day share is 10.7% - cleaner than 0% of that comparison set.

Los Angeles County Good-day share vs. every US county

Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release

10.7% 0th percentile higher than 0% of 951 US counties

0.0%–5.0%: 0 US counties (0%). Below this entry. 5.0%–10.0%: 1 US counties (0%). Below this entry. 10.0%–15.0%: 4 US counties (0%). This entry sits in this band. 15.0%–20.0%: 4 US counties (0%). Above this entry. 20.0%–25.0%: 1 US counties (0%). Above this entry. 25.0%–30.0%: 5 US counties (1%). Above this entry. 30.0%–35.0%: 9 US counties (1%). Above this entry. 35.0%–40.0%: 4 US counties (0%). Above this entry. 40.0%–45.0%: 16 US counties (2%). Above this entry. 45.0%–50.0%: 16 US counties (2%). Above this entry. 50.0%–55.0%: 32 US counties (3%). Above this entry. 55.0%–60.0%: 50 US counties (5%). Above this entry. 60.0%–65.0%: 77 US counties (8%). Above this entry. 65.0%–70.0%: 93 US counties (10%). Above this entry. 70.0%–75.0%: 109 US counties (11%). Above this entry. 75.0%–80.0%: 114 US counties (12%). Above this entry. 80.0%–85.0%: 123 US counties (13%). Above this entry. 85.0%–90.0%: 99 US counties (10%). Above this entry. 90.0%–95.0%: 117 US counties (12%). Above this entry. 95.0%–100.0%: 70 US counties (7%). Above this entry. 100.0%–105.0%: 7 US counties (1%). Above this entry. This county 0.0% 100% every floor-qualified US county, bucketed by value

Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.

Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025

Pollutant Breakdown

Days where each pollutant was the primary driver of AQI readings in Los Angeles County.

Los Angeles County, California criteria pollutant distribution Stratified-band visualization showing the share of monitored days each criteria pollutant (PM2.5, PM10, O3, NO2, CO) was the primary AQI driver. Ozone · 52.9% PM2.5 · 41.4% 0% 25% 50% 75% 100% Los Angeles County, California · 365 monitored days Criteria pollutant column
  • Ozone · 193 days · 52.9%
  • PM2.5 · 151 days · 41.4%
  • PM10 · 15 days · 4.1%
  • NO₂ · 6 days · 1.6%

2024 daily-monitor rhythm in Los Angeles County

Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). Jul posted the highest typical readings (median AQI 156, peak 230); Mar was cleanest at median 47. Summer months (Jun–Aug) averaged median AQI 138 vs 68 in Dec–Feb. 55 days crossed Unhealthy (AQI >150) at least once that year.

0 30 60 90 120 150 180 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 67 56 47 61 77 117 156 140 122 101 64 82
Los Angeles County median daily AQI by calendar month (2024, EPA daily county file)

Five-year seasonal record

EPA day-level county files · 2020–2024

1,827 daily readings show a recurring local pattern: Jul has the highest matched-month median AQI (135), while Mar is lowest (54). Each cell is that month’s median daily AQI, not a current-air forecast.

JanFebMarAprMayJunJulAugSepOctNovDec
2020 7366475690801291221581197983
2021 7163577180124112129101668472
2022 716862678011711511287716664
2023 64635573535916111290646369
2024 67564761771171561401221016482

Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.

Health Impact Assessment

Very Poor

Los Angeles County's air quality is rated Very Poor based on 10.7% good air days. There were 32 unhealthy days in 2025 when outdoor activity should be limited.

Air quality reached unhealthy levels on 32 days in 2025 (31 Unhealthy, 1 Very Unhealthy). Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, and adults over 65, should review the daily breakdown below and follow local air-quality advisories on high-AQI days.

Sensitive group advisory

People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.

The dominant pollutant is Ozone, driving AQI on 193 of 365 monitored days.

5-Year Air Quality Trend

Air quality is improving in Los Angeles County. Highest Good-day share: 2023 (11.3%, 41 of 365 monitored days).

Year Good Moderate USG Unhealthy Median AQI
2020 35 194 77 43 85
2021 9 259 70 26 79
2022 17 254 65 28 74
2023 41 237 52 32 67
2024 38 195 78 46 80
2025 39 228 66 31 74

How does Los Angeles County compare?

How Los Angeles County compares

Good-day share worse than typical
Los Angeles County 10.7%
Maricopa County, Arizona 8.8%
Typical US county 76.0%
Median AQI worse than typical
Los Angeles County 74
Maricopa County, Arizona 73
Typical US county 39
Unhealthy days / yr worse than typical
Los Angeles County 32
Maricopa County, Arizona 6
Typical US county 1

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.

Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Los Angeles County, California · 2020–2025

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Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.

Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.