Today | Weather | Sunday, August 9, 2026

Weather in Costa Mesa, California

04:34 AM
Now
Rainy Night
70° F
Feels Like 70°
Precipitation 45 %
Wind 4 mph
Humidity 89 %
Today
Cloudy Weather
Day 82°
Night 70°
Precipitation 0 %
Wind 8 mph
UV Index (0 - 11+) 10

Warning: High UV Index Today: 10

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.

Costa Mesa Weather Forecast Updated

39 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (August 9, 2025)
Cloudy Night

Day

73°

Night

64°

Wind

5 mph

Precipitation

0 %

Air Quality in Costa Mesa

NOW
37 AQI
Good air quality Dominant pollutant: PM2.5

Pollutant Concentrations:

PM2.5 8.99 µg/m³
PM10 27.11 µg/m³
O3 0.040 ppm
NO2 0.2 ppb
SO2 0.2 ppb
CO 0.06 ppm
NH3 0 µg/m³
NO 0 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)
PM2.58.99 µg/m³
PM1027.11 µg/m³
O377.77 µg/m³
NO20.46 µg/m³
SO20.64 µg/m³
CO72.22 µg/m³
NH30 µg/m³
NO0 µg/m³