Today | Weather | Saturday, August 29, 2026

Active Weather Warnings

Extreme Heat Warning

Weather in San Marcos, California

01:55 AM

Now

72° F

Feels Like 73°

Precipitation 0 %

Wind 4 mph

Humidity 90 %

Today

Day 93°

Night 68°

Precipitation 1 %

Wind 8 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.

San Marcos Weather Forecast Updated

33 minutes ago

Last updated on August 29, 2026 at 1:21 AM

Air Quality in San Marcos

NOW

96 AQI

Moderate air quality Dominant pollutant: PM_2.5

Pollutant Concentrations:

PM_2.5 33.62 µg/m³

PM₁₀ 48.12 µg/m³

O₃ 0.044 ppm

NO₂ 0.6 ppb

SO₂ 0.2 ppb

CO 0.13 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 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)

PM_2.5 – 33.62 µg/m³

PM₁₀ – 48.12 µg/m³

O₃ – 86.89 µg/m³

NO₂ – 1.07 µg/m³

SO₂ – 0.65 µg/m³

CO – 153.57 µg/m³

NH₃ – 0 µg/m³

NO – 0 µg/m³

View Hourly Air Quality Forecast

Weather Alerts and Warnings for San Marcos

Severe Expected Likely

Extreme Heat Warning

Extreme Heat Warning issued August 28 at 9:06PM PDT until August 29 at 8:00PM PDT by NWS San Diego CA

Aug 28, 9:06 PM → Aug 29, 8:00 PM

WHAT: Hot conditions continue into Saturday with high temperatures
up to 98 degrees. Lows will be in the low 70s.

WHERE: San Diego County Valleys.

WHEN: Until 8 PM PDT Saturday.

IMPACTS: Heat related illnesses increase significantly during
extreme heat events.

ADDITIONAL DETAILS: Temperatures will fall to below normal by
Sunday.

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Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.

Updated: Aug 29, 1:21 AM Source: NWS Alert