Today | Weather | Monday, July 20, 2026

Weather in San Mateo, California

02:21 PM
Now
Rainy Weather
73° F
Feels Like 73°
Precipitation 51 %
Wind 10 mph
UV Index (0 - 11+) 4
Humidity 58 %
Today
Partly Sunny with Showers
Day 73°
Night 57°
Precipitation 87 %
Wind 8 mph
UV Index (0 - 11+) 7

San Mateo Weather Forecast Updated

Last updated on
Weather Forecast History
Last Year's Weather on This Day (July 20, 2025)
Rainy Night

Day

72°

Night

55°

Wind

9 mph

Precipitation

45 %

Air Quality in San Mateo

NOW
35 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 3.69 µg/m³
PM10 9.25 µg/m³
O3 0.038 ppm
NO2 0.3 ppb
SO2 0.3 ppb
CO 0.08 ppm
NH3 0 µg/m³
NO 0.08 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)
PM2.53.69 µg/m³
PM109.25 µg/m³
O374.93 µg/m³
NO20.58 µg/m³
SO20.79 µg/m³
CO88.61 µg/m³
NH30 µg/m³
NO0.08 µg/m³