Today | Weather | Thursday, December 11, 2025

Weather in San Mateo, California

05:50 AM
Now
Cloudy Night
43° F
Feels Like 41°
Precipitation 0 %
Wind 6 mph
Humidity 98 %
Today
Cloudy Weather
Day 61°
Night 43°
Precipitation 0 %
Wind 6 mph
UV Index (0 - 11+) 2

San Mateo Weather Forecast Updated

23 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (December 11, 2024)
Rainy Weather

Day

59°

Night

52°

Wind

11 mph

Precipitation

94 %

Air Quality in San Mateo

NOW
56 AQI
Moderate air quality Dominant pollutant: PM2.5

Pollutant Concentrations:

PM2.5 14.89 µg/m³
PM10 23.28 µg/m³
O3 0.018 ppm
NO2 10.6 ppb
SO2 1 ppb
CO 0.26 ppm
NH3 0.69 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 acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.

Show raw pollutant concentrations (µg/m³)
PM2.514.89 µg/m³
PM1023.28 µg/m³
O335.73 µg/m³
NO219.92 µg/m³
SO22.6 µg/m³
CO302.08 µg/m³
NH30.69 µg/m³
NO0 µg/m³