Today | Weather | Tuesday, April 21, 2026

Weather in Costa Mesa, California

03:25 PM
Now
Cloudy Weather
68° F
Feels Like 72°
Precipitation 34 %
Wind 10 mph
UV Index (0 - 11+) 6
Humidity 64 %
Today
Partly Sunny with Showers
Day 70°
Night 55°
Precipitation 87 %
Wind 8 mph
UV Index (0 - 11+) 6

Costa Mesa Weather Forecast Updated

Last updated on
Weather Forecast History
Last Year's Weather on This Day (April 21, 2025)
Cloudy Weather

Day

66°

Night

55°

Wind

7 mph

UV Index

10

Precipitation

0 %

Air Quality in Costa Mesa

NOW
43 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 1.99 µg/m³
PM10 4.46 µg/m³
O3 0.046 ppm
NO2 0.1 ppb
SO2 0.1 ppb
CO 0.11 ppm
NH3 0 µg/m³
NO 0.01 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)
PM2.51.99 µg/m³
PM104.46 µg/m³
O390.79 µg/m³
NO20.1 µg/m³
SO20.22 µg/m³
CO121.03 µg/m³
NH30 µg/m³
NO0.01 µg/m³