Today | Weather | Sunday, December 14, 2025

Weather in San Mateo, California

05:14 AM
Now
Foggy Weather
45° F
Feels Like 43°
Precipitation 0 %
Wind 5 mph
Humidity 100 %
Today
Cloudy Weather
Day 55°
Night 43°
Precipitation 0 %
Wind 6 mph
UV Index (0 - 11+) 2

San Mateo Weather Forecast Updated

Last updated on
Weather Forecast History
Last Year's Weather on This Day (December 14, 2024)
Cloudy Night

Day

57°

Night

45°

Wind

4 mph

Precipitation

1 %

Air Quality in San Mateo

NOW
39 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 7.81 µg/m³
PM10 13.24 µg/m³
O3 0.042 ppm
NO2 0.5 ppb
SO2 0.4 ppb
CO 0.10 ppm
NH3 0 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)
PM2.57.81 µg/m³
PM1013.24 µg/m³
O382.81 µg/m³
NO20.91 µg/m³
SO21.06 µg/m³
CO115.16 µg/m³
NH30 µg/m³
NO0 µg/m³