Extreme Heat risk in California

Extreme Heat in California: What to Know

California is no stranger to hot weather, but extreme heat events—periods of abnormally high temperatures lasting multiple days—are a growing hazard across the state. The California Governor's Office of Emergency Services lists extreme heat as a significant risk due to its frequency, widespread geographic reach, and impact on public health, infrastructure, and the economy. The state’s rating of 4 out of 5 for this hazard reflects that risk.

Geography matters immensely. Coastal areas like San Francisco and San Diego typically enjoy milder summer temperatures thanks to ocean breezes, but just a few miles inland, temperatures can soar. The Central Valley—including cities like Sacramento, Fresno, and Bakersfield—often sees triple-digit heat, as do the Mojave and Colorado Deserts. Even urban centers like Los Angeles and San Jose experience the “urban heat island” effect, where concrete, asphalt, and limited green space trap heat and make nights uncomfortably warm.

Heat waves in California are most common from May through October, with the peak occurring between July and September. These events can be exacerbated by high-pressure ridges that park over the West, bringing prolonged sunny, stagnant air. Climate trends suggest that extreme heat will become more frequent, longer-lasting, and more intense in the coming decades, making preparedness essential for all residents.

How It Affects Homes

Extreme heat can stress your home in several ways, even though it rarely causes the dramatic damage associated with floods or earthquakes. Instead, the effects build over time and can be costly.

Property damage: Prolonged exposure to high temperatures can degrade roofing materials, causing shingles to curl, crack, or lose granules. Wood siding and window frames can warp or expand, leading to gaps and drafts. Extreme heat also accelerates the aging of sealants, gaskets, and appliances, particularly those in attics or near heat-producing equipment. Electronics and home wiring can overheat and malfunction if not properly ventilated.

Your HVAC system takes a beating during heat waves. An overworked air conditioner may fail at the worst possible time, leaving your home dangerously hot. Power outages are also more likely during heat waves because high demand strains the electric grid. Without cooling, indoor temperatures can quickly become unsafe, especially for older adults and young children.

Insurance considerations: Standard homeowners insurance policies do not typically cover damage caused directly by extreme heat, such as warped siding or a failed AC compressor. However, heat can contribute to other covered perils—for example, a wildfire near your home can be covered under your policy’s fire provisions. Review your policy with your insurer to understand what is and isn’t covered, and keep records of maintenance to support any future claims. Flooding from dried-out soils or cracked pipes after heat waves may be covered only if you have separate flood insurance.

The best way to protect your home from heat is to prevent damage before it happens. Focus on making your home more resilient, improving efficiency, and preparing for potential power outages.

How to Prepare Your Home

• Seal and insulate. Use caulk and weatherstripping to seal gaps around doors and windows. Add insulation to your attic to keep hot air out and cool air in.
• Reflect heat. Install reflective barriers or cool roofs to bounce sunlight away from your home. Light-colored exterior paint and roofing can also reduce heat gain.
• Shade your home. Plant trees strategically to shade windows and walls—deciduous trees give shade in summer and lose leaves in winter. Awnings, shade sails, and exterior blinds help block direct sun.
• Install window coverings. Use reflective window film, blackout curtains, or cellular shades to reduce solar heat gain, especially on south- and west-facing windows.
• Maintain your HVAC. Have your air conditioner serviced before summer. Replace filters regularly, ensure ducts are sealed, and consider a smart thermostat to manage cooling efficiently.
• Use fans and natural ventilation. Ceiling fans and portable fans help circulate air. Open windows overnight when the outdoor temperature drops, and close them in the morning to trap cool air.
• Provide backup power. A portable generator or solar power system with battery backup can keep your AC or fans running during an outage. Never run a generator indoors.
• Store water. Have at least three days of drinking water (one gallon per person per day) and extra for pets. Also fill bathtubs or containers for flushing toilets if water service fails.
• Create a cool zone. Designate one room as your “cool room” with AC, fans, and window shades. Make it comfortable and safe for the whole household.
• Prepare an emergency kit. Include flashlights, batteries, a battery-powered radio, medications, and a cooler or ice packs for storing perishables.

Frequently Asked Questions

How hot does it get in California?

Summer temperatures in the Central Valley and desert regions routinely exceed 100°F, and during intense heat waves they can reach 110°F or higher. Coastal cities rarely see such highs, but inland neighborhoods can experience extreme heat even on days when the coast feels mild. Heat waves lasting several days have become increasingly common in recent decades.

Is extreme heat considered a natural disaster for insurance?

Extreme heat itself is not typically treated as a declared natural disaster for insurance purposes, and direct damage from high temperatures—like heat-warped siding or a broken air conditioner—is generally excluded from standard homeowners policies. However, related events such as wildfires or power outages may trigger coverage depending on your policy. Check with your insurance agent to understand what is covered.

What should I do if my power goes out during a heat wave?

Move to the coolest room in your home, use battery-powered fans if available, and close shades to block sun. Drink water regularly and wear lightweight clothing. If indoor temperatures become unsafe—above 85°F for several hours—go to a public cooling center, shopping mall, or other air-conditioned place. Never use a gas stove or oven to cool your home, and avoid opening windows unless the outdoor air is cooler.

Official Resources

• California Governor's Office of Emergency Services
• National Weather Service - Heat Safety
• Ready.gov - Extreme Heat
• CDC - About Extreme Heat