Today | Weather | Monday, July 20, 2026

Active Weather Warnings

High Surf Advisory

Weather in Costa Mesa, California

02:57 AM

Now

68° F

Feels Like 66°

Precipitation 0 %

Wind 5 mph

Humidity 92 %

Today

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

26 minutes ago

Last updated on July 20, 2026 at 2:31 AM

Weather Forecast History

Last Year's Weather on This Day (July 20, 2025)

Day

75°

Night

66°

Wind

6 mph

Precipitation

1 %

Air Quality in Costa Mesa

NOW

35 AQI

Good air quality Dominant pollutant: O₃

Pollutant Concentrations:

PM_2.5 4.37 µg/m³

PM₁₀ 13.8 µg/m³

O₃ 0.038 ppm

NO₂ 0.2 ppb

SO₂ 0.3 ppb

CO 0.07 ppm

NH₃ 0 µg/m³

NO 0 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 – 4.37 µg/m³

PM₁₀ – 13.8 µg/m³

O₃ – 74.11 µg/m³

NO₂ – 0.44 µg/m³

SO₂ – 0.79 µg/m³

CO – 85.01 µg/m³

NH₃ – 0 µg/m³

NO – 0 µg/m³

View Hourly Air Quality Forecast

Weather Alerts and Warnings for Costa Mesa

Minor Expected Likely

High Surf Advisory

High Surf Advisory issued July 19 at 8:19PM PDT until July 21 at 11:00PM PDT by NWS San Diego CA

Jul 19, 8:19 PM → Jul 21, 11:00 PM

WHAT: Large breaking waves of 4 to 7 feet with sets up to 8
feet at south or southwest facing beaches.

WHERE: San Diego County Coastal Areas and Orange County
Coastal Areas.

WHEN: Until 11 PM PDT Tuesday.

IMPACTS: Dangerous swimming and surfing conditions and
localized beach erosion.

ADDITIONAL DETAILS: South swell of 4 to 5 feet with a period of
12-13 seconds generating high surf, primarily for south- facing
beaches. High risk of rip currents exists with high surf and
strong longshore currents are expected on west-facing beaches.
High tides will generally be at or below 5.5 feet, but localized
areas of beach erosion and minor tidal overflow may occur with
the high surf during high tides. Swell and surf will decrease
late Tuesday into Wednesday.

+ Read More

Inexperienced swimmers should remain out of the water due to dangerous surf conditions.

Updated: Jul 20, 2:31 AM Source: NWS Alert