Today | Weather | Thursday, August 21, 2025

Heat Advisory (Issued when high temperatures and humidity create conditions that may be hazardous during outdoor activity or prolonged exposure.)

Weather in San Mateo, California

10:29 PM

Now

63° F

Feels Like 61°

Precipitation 0 %

Wind 10 mph

Humidity 78 %

Today

Day 91°

Night 57°

Precipitation 0 %

Wind 9 mph

Other:

Partly overcast.

San Mateo Weather Forecast Updated

42 minutes ago

Last updated on August 21, 2025 9:47 PM

Last Year's Weather on This Day (August 21, 2024)

73°

59°

NOW

52 AQI

Moderate air quality Dominant pollutant: PM2.5

PM2.5 11.69 µg/m³

PM10 28.56 µg/m³

O₃ 24.57 ppb

NO₂ 14.07 ppb

SO₂ 0.47 ppb

CO 201.96 ppb

PM_2.5 – Fine particles <2.5μm

PM₁₀ – Inhalable particles <10μm

O₃ – Ozone

NO₂ – Nitrogen dioxide

SO₂ – Sulfur dioxide

CO – Carbon monoxide

Air quality is currently in the acceptable range. However, sensitive individuals should be aware of potential risks from certain pollutants.