Today | Weather | Saturday, September 19, 2026

Weather in Costa Mesa, California

01:46 AM
Now
Cloudy Night
64° F
Feels Like 63°
Precipitation 0 %
Wind 5 mph
Humidity 87 %
Today
Cloudy Weather
Day 79°
Night 64°
Precipitation 0 %
Wind 7 mph
UV Index (0 - 11+) 7

Costa Mesa Weather Forecast Updated

6 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (September 19, 2025)
Cloudy Night

Day

81°

Night

63°

Wind

5 mph

Precipitation

3 %

Air Quality in Costa Mesa

NOW
44 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 8.01 µg/m³
PM10 25.06 µg/m³
O3 0.047 ppm
NO2 0.2 ppb
SO2 0.3 ppb
CO 0.13 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)
PM2.58.01 µg/m³
PM1025.06 µg/m³
O392.64 µg/m³
NO20.39 µg/m³
SO20.71 µg/m³
CO149.6 µg/m³
NH30 µg/m³
NO0 µg/m³