Today | Weather | Thursday, September 4, 2025

Weather in Costa Mesa, California

10:34 AM

Now

77° F

Feels Like 79°

Precipitation 0 %

Wind 7 mph

UV Index (0 - 11+) 11

Humidity 68 %

Today

Day 81°

Night 64°

Precipitation 0 %

Wind 8 mph

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:

Some cloud cover, then sun.

Costa Mesa Weather Forecast Updated

43 minutes ago

Last updated on September 04, 2025 9:50 AM

Air quality in Costa Mesa

NOW

51 AQI

Moderate air quality Dominant pollutant: PM2.5

Pollutant Concentrations:

PM2.5 10.66 µg/m³

PM10 28.79 µg/m³

O₃ 19.78 ppb

NO₂ 20.03 ppb

SO₂ 0.78 ppb

CO 471.33 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:

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

View Hourly Air Quality Forecast