Today | Weather | Thursday, January 8, 2026

Weather in San Marcos, California

03:20 AM
Now
Cloudy Night
48° F
Feels Like 48°
Precipitation 3 %
Wind 5 mph
Humidity 97 %
Today
Cloudy Weather
Day 63°
Night 36°
Precipitation 14 %
Wind 7 mph
UV Index (0 - 11+) 3

San Marcos Weather Forecast Updated

17 minutes ago
Last updated on

Air Quality in San Marcos

NOW
41 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 3.79 µg/m³
PM10 15.74 µg/m³
O3 0.044 ppm
NO2 0.3 ppb
SO2 0.1 ppb
CO 0.11 ppm
NH3 0.05 µg/m³
NO 0 µg/m³
PM2.5 – Fine particles <2.5μm
PM10 – Inhalable particles <10μm
O3 – Ozone
NO2 – Nitrogen dioxide
SO2 – Sulfur dioxide
CO – Carbon monoxide
NH3 – Ammonia
NO – Nitric oxide

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

Show raw pollutant concentrations (µg/m³)
PM2.53.79 µg/m³
PM1015.74 µg/m³
O386.68 µg/m³
NO20.61 µg/m³
SO20.37 µg/m³
CO130.01 µg/m³
NH30.05 µg/m³
NO0 µg/m³