Today | Weather | Thursday, September 11, 2025

Weather in San Mateo, California

04:03 AM

Now

63° F

Feels Like 61°

Precipitation 7 %

Wind 8 mph

Humidity 89 %

Today

Day 73°

Night 61°

Precipitation 5 %

Wind 16

UV Index (0 - 11+) 11

Warning: Extreme UV Index Today: 11+

Overexposure to the sun's harmful UV rays can cause sunburn and increase the risk of developing skin cancer, including melanoma. Protect yourself by wearing clothing that covers your skin, sunglasses, and a hat. Apply a broad-spectrum sunscreen with an SPF of 30 or higher every two hours, even on cloudy days. Minimize direct sun exposure during peak hours (10 AM to 4 PM) to reduce the risk.

Other:

Clouds giving way to sun with a twist.

San Mateo Weather Forecast Updated

Last updated on September 11, 2025 2:56 AM

Air quality in San Mateo

NOW

34 AQI

Good air quality Dominant pollutant: PM2.5

Pollutant Concentrations:

PM2.5 9.86 µg/m³

PM10 13.88 µg/m³

O₃ 30.20 ppb

NO₂ 2.81 ppb

SO₂ 0.66 ppb

CO 133.05 ppb

PM_2.5 – Fine particles <2.5μm

PM₁₀ – Inhalable particles <10μm

O₃ – Ozone

NO₂ – Nitrogen dioxide

SO₂ – Sulfur dioxide

CO – Carbon monoxide

Health Recommendations:

With this level of air quality, you have no limitations. Enjoy the outdoors

View Hourly Air Quality Forecast