Today | Weather | Monday, April 27, 2026

Weather in Costa Mesa, California

05:53 PM
Now
Cloudy Weather
63° F
Feels Like 63°
Precipitation 0 %
Wind 10 mph
UV Index (0 - 11+) 2
Humidity 57 %
Today
Cloudy Weather
Day 66°
Night 54°
Precipitation 9 %
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

28 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (April 27, 2025)
Cloudy Weather

Day

64°

Night

55°

Wind

7 mph

UV Index

6

Precipitation

25 %

Air Quality in Costa Mesa

NOW
82 AQI
Moderate air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 1.35 µg/m³
PM10 3.18 µg/m³
O3 0.064 ppm
NO2 0.1 ppb
SO2 0.1 ppb
CO 0.11 ppm
NH3 0 µg/m³
NO 0.02 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 acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.

Show raw pollutant concentrations (µg/m³)
PM2.51.35 µg/m³
PM103.18 µg/m³
O3126.38 µg/m³
NO20.19 µg/m³
SO20.39 µg/m³
CO126.16 µg/m³
NH30 µg/m³
NO0.02 µg/m³