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)
66
Moderate
San Marcos, California
Last updated: ... (Local time)

Good
Fine
Moderate
Poor
Very poor
Hazardous
16.95 μg/m³
0
12.1
35.5
55.5
250.5
500.5+
75.24 μg/m³
0
55
155
255
425
605+
50.33 ppb
0
55
71
86
201
201+
1.33 ppb
0
36
76
186
605
1005+
7.02 ppb
0
54
101
361
1250
2050+
0.16 ppm
0
4.5
9.5
12.5
230.5
50.5+
Pollen Level
Moderate
San Marcos, California
San Marcos, California
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AQI 71
Moderate
5.23μg/m³
PM2.5
22.18μg/m³
PM10
61.06ppb
O3
0.82ppb
SO2
5.89ppb
NO2
0.32ppm
CO
AQI 50
Good
4.70μg/m³
PM2.5
34.16μg/m³
PM10
54.49ppb
O3
0.83ppb
SO2
12.50ppb
NO2
0.32ppm
CO
AQI 61
Moderate
3.60μg/m³
PM2.5
24.23μg/m³
PM10
58.30ppb
O3
0.81ppb
SO2
3.82ppb
NO2
0.32ppm
CO
AQI 51
Moderate
3.85μg/m³
PM2.5
31.85μg/m³
PM10
54.85ppb
O3
0.84ppb
SO2
7.25ppb
NO2
0.32ppm
CO
AQI 58
Moderate
8.33μg/m³
PM2.5
37.97μg/m³
PM10
57.30ppb
O3
0.87ppb
SO2
6.77ppb
NO2
0.33ppm
CO
AQI 50
Good
3.50μg/m³
PM2.5
23.70μg/m³
PM10
54.39ppb
O3
0.84ppb
SO2
12.38ppb
NO2
0.32ppm
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 12:00:00 on 2026-10-06.
The best air quality in San Marcos, California was recorded at 03:00:00 on 2026-10-05.
The real-time air quality index in San Marcos, California is 51, currently categorized as Moderate.
The most common pollutant in San Marcos, California is O3.
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 4.906 μg/m3.
The current PM10 levels in San Marcos, California are 22.18 μg/m3.
The current carbon monoxide (CO) level in San Marcos, California is 0.32 ppm.
The current sulfur dioxide (SO2) levels in San Marcos, California are 0.826 ppb.
The current ozone (O3) levels at San Marcos, California is 54.75 ppm.
The current nitrogen dioxide (NO2) levels at San Marcos, California is 7.285 ppb.
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