Today | Weather | Saturday, August 29, 2026

Active Weather Warnings

Heat Advisory

Weather in Costa Mesa, California

11:22 AM

Now

84° F

Feels Like 95°

Precipitation 0 %

Wind 7 mph

UV Index (0 - 11+) 6

Humidity 64 %

Today

Day 86°

Night 72°

Precipitation 0 %

Wind 7 mph

UV Index (0 - 11+) 9

Warning: High UV Index Today: 9

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

52 minutes ago

Last updated on August 29, 2026 at 10:29 AM

Weather Forecast History

Last Year's Weather on This Day (August 29, 2025)

Day

84°

Night

66°

Wind

5 mph

Precipitation

0 %

Air Quality in Costa Mesa

NOW

31 AQI

Good air quality Dominant pollutant: O₃

Pollutant Concentrations:

PM_2.5 6.65 µg/m³

PM₁₀ 23.69 µg/m³

O₃ 0.034 ppm

NO₂ 0.3 ppb

SO₂ 0.2 ppb

CO 0.07 ppm

NH₃ 0 µg/m³

NO 0.13 µg/m³

PM_2.5 – 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)

PM_2.5 – 6.65 µg/m³

PM₁₀ – 23.69 µg/m³

O₃ – 65.93 µg/m³

NO₂ – 0.55 µg/m³

SO₂ – 0.63 µg/m³

CO – 81.02 µg/m³

NH₃ – 0 µg/m³

NO – 0.13 µg/m³

View Hourly Air Quality Forecast

Weather Alerts and Warnings for Costa Mesa

Moderate Expected Likely

Heat Advisory

Heat Advisory issued August 29 at 5:20AM PDT until August 29 at 8:00PM PDT by NWS San Diego CA

Aug 29, 5:20 AM → Aug 29, 8:00 PM

WHAT: Temperatures 82 to 88.

WHERE: Orange County Coastal Areas.

WHEN: Until 8 PM PDT this evening.

IMPACTS: Hot temperatures may cause heat illnesses.

+ Read More

Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.

Updated: Aug 29, 10:29 AM Source: NWS Alert