Stay updated with real-time air quality in San Marcos, California featuring accurate data on AQI, PM2.5, PM10, O3, NO2, SO2, and CO levels. Use our interactive map and detailed forecasts to monitor pollution trends, manage health risks, and plan your daily activities with confidence.
Live AQI (Air Quality Index)
56
Moderate
San Marcos, California
Last updated: ... (Local time)

Good
Fine
Moderate
Poor
Very poor
Hazardous
12.10 μg/m³
0
12.1
35.5
55.5
250.5
500.5+
32.14 μg/m³
0
55
155
255
425
605+
43.33 ppb
0
55
71
86
201
201+
0.79 ppb
0
36
76
186
605
1005+
3.92 ppb
0
54
101
361
1250
2050+
0.18 ppm
0
4.5
9.5
12.5
230.5
50.5+
Pollen Level
Moderate
San Marcos, California
San Marcos, California
Scroll To Air Quality MapLoading...
AQI 54
Moderate
10.74μg/m³
PM2.5
25.31μg/m³
PM10
42.26ppb
O3
0.70ppb
SO2
5.23ppb
NO2
0.18ppm
CO
AQI 52
Moderate
10.32μg/m³
PM2.5
29.50μg/m³
PM10
40.01ppb
O3
0.66ppb
SO2
7.59ppb
NO2
0.18ppm
CO
AQI 49
Good
9.09μg/m³
PM2.5
39.81μg/m³
PM10
45.32ppb
O3
0.71ppb
SO2
4.11ppb
NO2
0.18ppm
CO
AQI 49
Good
9.43μg/m³
PM2.5
34.12μg/m³
PM10
39.08ppb
O3
0.69ppb
SO2
7.92ppb
NO2
0.18ppm
CO
AQI 49
Good
8.83μg/m³
PM2.5
23.61μg/m³
PM10
39.15ppb
O3
0.65ppb
SO2
4.01ppb
NO2
0.18ppm
CO
AQI 49
Good
9.38μg/m³
PM2.5
34.09μg/m³
PM10
39.00ppb
O3
0.70ppb
SO2
7.81ppb
NO2
0.18ppm
CO
Air quality measurements for California, USA meet strict US EPA standards. These measurements are collected from reliable sources, including satellites and ground-based monitoring systems. Advanced algorithms and machine learning techniques are applied to the data, factoring in variables such as traffic and population density, to ensure precision and reliability.
Source: Ambee Data Sources
Air quality data for San Marcos, California is updated on an hourly basis.
The worst air quality in San Marcos, California was recorded at 06:00:00 on 2026-06-08.
The best air quality in San Marcos, California was recorded at 11:00:00 on 2026-06-08.
The real-time air quality index in San Marcos, California is 52, currently categorized as Moderate.
The most common pollutant in San Marcos, California is PM2.5.
If the air quality in San Marcos, California is poor, limit outdoor activities and use a mask to safeguard your health.
The measured PM2.5 levels in San Marcos, California at present are 10.453 μg/m3.
The current PM10 levels in San Marcos, California are 38.119 μg/m3.
The current carbon monoxide (CO) level in San Marcos, California is 0.18 ppm.
The current sulfur dioxide (SO2) levels in San Marcos, California are 0.683 ppb.
The current ozone (O3) levels at San Marcos, California is 44.698 ppm.
The current nitrogen dioxide (NO2) levels at San Marcos, California is 7.657 ppb.
All Rights Reserved © Ambee Inc. 2025