How Peninsula Fog Affects Your HVAC System

The Marine Layer Effect

That famous Peninsula fog brings more than cool mornings. The marine layer affects your HVAC system in several ways.

Humidity Challenges

Morning Moisture

• Fog increases indoor humidity
• Can promote mold and mildew
• Affects comfort even when temperatures are mild

Afternoon Drying

• Rapid humidity changes as fog burns off
• Indoor air can swing from humid to dry
• Puts stress on HVAC components

Impact on Your AC

Outdoor Unit

• Moisture on coils can attract dirt
• Corrosion risk on coastal areas
• Fins may need more frequent cleaning

Indoor Air Quality

• Higher humidity can worsen allergies
• Mold spores thrive in damp conditions
• Proper dehumidification becomes important

What You Can Do

Dehumidification

• Run your AC to remove humidity
• Consider a whole-home dehumidifier
• Use bathroom fans during foggy mornings

Outdoor Unit Care

• Rinse coils more frequently
• Check for corrosion signs
• Consider protective coatings for coastal homes

Indoor Air Quality

• Use MERV 8+ filters
• Consider UV air purifiers
• Address any musty smells promptly

The Upside of Fog

Peninsula fog actually helps your HVAC system:

• Natural cooling reduces AC needs
• Lower daytime temperatures
• Less strain on equipment during summer

Location Matters

• Coastal areas (Pacifica, Half Moon Bay): More fog impact
• Inland Peninsula (Palo Alto, Mountain View): Less fog, more heat
• Mid-Peninsula (San Mateo, Redwood City): Variable conditions