Today | Weather | Monday, April 27, 2026

Weather in San Mateo, California

10:36 AM
Now
Cloudy Weather
59° F
Feels Like 57°
Precipitation 7 %
Wind 8 mph
UV Index (0 - 11+) 2
Humidity 65 %
Today
Cloudy Weather
Day 64°
Night 50°
Precipitation 25 %
Wind 9 mph
UV Index (0 - 11+) 8

Warning: High UV Index Today: 8

High risk of harm from unprotected sun exposure. Take precautions: wear a hat, sunglasses, and apply sunscreen regularly if you’ll be outdoors for extended periods.

San Mateo Weather Forecast Updated

4 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (April 27, 2025)
Cloudy Weather

Day

59°

Night

48°

Wind

11 mph

UV Index

2

Precipitation

25 %

Air Quality in San Mateo

NOW
61 AQI
Moderate air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 1.91 µg/m³
PM10 5.57 µg/m³
O3 0.057 ppm
NO2 0.2 ppb
SO2 0.2 ppb
CO 0.11 ppm
NH3 0 µg/m³
NO 0.04 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)
PM2.51.91 µg/m³
PM105.57 µg/m³
O3112.88 µg/m³
NO20.36 µg/m³
SO20.59 µg/m³
CO131.32 µg/m³
NH30 µg/m³
NO0.04 µg/m³