How Hot Can a Car Get in the Sun

On a sunny 70°F day, your car’s interior can soar past 110°F within an hour—hot enough to cause serious harm. This guide explains the science behind extreme heat buildup, real-world dangers, and practical ways to protect yourself, pets, and your vehicle.

Key Takeaways

• Car interiors heat up fast: Temperatures can rise 40°F or more in just 10 minutes on a mild sunny day.
• Even cool days are risky: A car can reach dangerous levels on days as cool as 60°F if the sun is shining.
• Pets and kids are most vulnerable: Heatstroke can occur in minutes, even with windows cracked.
• Dark interiors absorb more heat: Black dashboards and seats can hit 180°F or higher.
• Parking strategies matter: Shade, sunshades, and ventilation reduce peak temperatures significantly.
• Long-term damage is real: Excessive heat degrades electronics, upholstery, and battery life.
• Prevention is simple and effective: Small habits like using a windshield cover or parking smart save lives and extend car life.

How Hot Can a Car Get in the Sun?

Imagine stepping into your car after it’s been parked outside on a sunny afternoon. The steering wheel burns your hands. The seat feels like a sauna. The air is thick and hard to breathe. You crank the AC, but it takes minutes to cool down. Now imagine that same car on a 90°F day—or worse, with a child or pet inside.

This isn’t just about discomfort. It’s about safety. The truth is, cars can get dangerously hot in the sun—far hotter than the outside air temperature. Understanding how and why this happens can help you protect your loved ones, your pets, and your vehicle.

In this guide, we’ll break down the science behind car heat buildup, explore real-world temperature extremes, and share practical tips to keep your car cooler and safer. Whether you’re a parent, pet owner, or just someone who wants to protect their investment, this information could save a life—or at least make your summer drives a lot more pleasant.

The Science of Heat Buildup in Cars

So, why do cars get so hot when left in the sun? It all comes down to basic physics: the greenhouse effect.

When sunlight hits your car, it passes through the windows as visible light. This light is absorbed by the seats, dashboard, steering wheel, and floor—especially if they’re dark-colored. Once absorbed, the energy is re-radiated as infrared heat (thermal energy). But here’s the problem: that heat can’t easily escape back out through the glass. The windows act like a barrier, trapping the heat inside—just like a greenhouse.

This process is known as solar gain. The more direct sunlight your car receives, the more heat builds up. And because cars are enclosed spaces with poor airflow, the temperature rises quickly and stays high.

Factors That Influence Interior Temperature

Several factors determine how hot your car gets:

• Outside air temperature: Obviously, hotter days lead to hotter cars. But even mild days can be dangerous.
• Sun exposure: Direct sunlight is the biggest contributor. A car in full sun will heat up much faster than one in partial shade.
• Color of the car and interior: Dark colors absorb more heat. A black car with a black interior will get significantly hotter than a white car with light-colored seats.
• Windows and tinting: Tinted windows can reduce heat slightly, but they don’t stop the greenhouse effect. Cracking windows helps a little with airflow, but not enough to prevent dangerous temperatures.
• Parking surface: Asphalt and concrete absorb and radiate heat, warming the car from below. Parking on grass or gravel can reduce this effect slightly.
• Duration of exposure: The longer a car sits in the sun, the hotter it gets. Most of the temperature rise happens in the first hour.

Real-World Temperature Data

Studies have shown just how extreme car temperatures can become. The Arizona Department of Health Services conducted a well-known experiment in which they measured the interior temperature of a car parked in the sun.

On a day when the outside temperature was 80°F, the car’s interior reached:

• 104°F within 20 minutes
• 114°F within 40 minutes
• 123°F after one hour

And that was on an 80°F day. On a 90°F day, the same car hit 140°F in just one hour. The dashboard and steering wheel can exceed 180°F—hot enough to cause third-degree burns on contact.

Even more alarming: on a relatively cool 60°F day with full sun, a car’s interior can still reach 110°F in under an hour. This means danger isn’t limited to summer heatwaves. Spring and early fall days can be just as risky.

Dangers of Extreme Heat in Cars

High temperatures inside a car aren’t just uncomfortable—they’re potentially deadly. The risks affect people, pets, and even the vehicle itself.

Health Risks for People

When a person is trapped in a hot car, their body temperature rises rapidly. Normal body temperature is around 98.6°F. When it climbs above 104°F, heatstroke can occur—leading to confusion, seizures, loss of consciousness, and even death.

Children are especially vulnerable. Their bodies heat up three to five times faster than adults. According to KidsAndCars.org, over 900 children in the U.S. have died from heatstroke after being left in hot cars since 1998. Most of these tragedies happen when a parent or caregiver forgets a child in the back seat.

Symptoms of heatstroke include:

• Hot, dry skin or profuse sweating
• Rapid pulse
• Dizziness or confusion
• Nausea or vomiting
• Loss of consciousness

Even short exposures can be dangerous. A child can suffer heatstroke in as little as 10 minutes on a warm day.

Pet Safety and Heatstroke

Pets are just as at risk—if not more so. Dogs, in particular, can’t sweat like humans. They cool themselves by panting, but in a hot car, this isn’t enough.

A dog left in a car on an 80°F day can suffer heatstroke in under 30 minutes. Symptoms include excessive panting, drooling, vomiting, lethargy, and collapse. Without immediate treatment, it can be fatal.

Never leave a pet unattended in a parked car—even with the windows cracked or for “just a few minutes.” The temperature inside can rise quickly, and pets don’t have the ability to escape or call for help.

Damage to Your Vehicle

Extreme heat doesn’t just harm living beings—it damages your car too.

• Interior materials: Prolonged exposure to high heat can cause leather seats to crack, vinyl dashboards to warp, and plastic components to degrade.
• Electronics: Car stereos, GPS units, and infotainment systems can overheat and malfunction. Batteries may lose charge faster in extreme heat.
• Fluids and lubricants: Engine oil, transmission fluid, and brake fluid can break down faster when exposed to high temperatures, reducing their effectiveness.
• Tires: Heat can cause tire pressure to increase, raising the risk of blowouts—especially on long drives.
• Air quality: Heat can cause chemicals in adhesives, plastics, and upholstery to off-gas, releasing volatile organic compounds (VOCs) that can affect air quality inside the car.

Over time, repeated heat exposure can shorten the lifespan of your vehicle and lead to costly repairs.

How Long Does It Take for a Car to Heat Up?

One of the most surprising facts about car heat is how quickly it builds up.

Studies show that the temperature inside a parked car can rise by 20°F in just the first 10 minutes. After 30 minutes, it can increase by 30–40°F. And within one hour, it can be 40–50°F hotter than the outside air.

Here’s a breakdown based on real data:

• 10 minutes: +20°F
• 20 minutes: +30°F
• 30 minutes: +40°F
• 60 minutes: +45–50°F

This means that on a 75°F day, your car could reach 120°F in just one hour. On a 90°F day, it could hit 140°F.

And remember: this happens even if you crack the windows. Opening windows by an inch or two does very little to reduce heat buildup. In fact, some studies show it may increase airflow slightly, but not enough to make a meaningful difference in temperature.

The Myth of “Just a Few Minutes”

Many people believe it’s safe to leave a child or pet in a car for “just a few minutes.” But as we’ve seen, temperatures rise fast—and so does the risk.

A child’s body temperature can reach dangerous levels in under 10 minutes. A dog can suffer heatstroke in 20–30 minutes. And once heatstroke begins, every second counts.

There’s no safe amount of time to leave a living being in a hot car—even if it’s “only for a quick errand.” The best rule? Never leave a child or pet unattended in a vehicle.

How to Keep Your Car Cooler in the Sun

The good news? There are simple, effective ways to reduce heat buildup and protect your car, passengers, and pets.

Use a Windshield Sunshade

A reflective sunshade placed on the windshield can reduce interior temperatures by up to 40°F. It blocks direct sunlight from hitting the dashboard and seats, slowing down heat absorption.

Look for a high-quality, reflective shade that fits your windshield snugly. Some even have built-in suction cups or foldable designs for easy storage.

Park in the Shade

Whenever possible, park in the shade—under a tree, in a garage, or in a covered parking area. Even partial shade can make a big difference.

If shade isn’t available, try to park so that the front of the car faces away from the sun. This reduces direct sunlight on the windshield, which is the main entry point for solar heat.

Use Window Tinting (Carefully)

Tinted windows can reduce heat by blocking some of the sun’s infrared rays. However, they’re not a cure-all. Most standard tints only reduce interior temperatures by 5–10°F.

Be aware of local laws—some states restrict how dark your windows can be. Also, avoid cheap tints that can bubble or peel over time.

Crack the Windows (Slightly)

While cracking windows doesn’t prevent dangerous heat buildup, it can help a little by allowing some hot air to escape. Open them about half an inch—enough for airflow, but not so much that it invites theft or rain.

Just don’t rely on this as a safety measure. It’s not enough to protect a child or pet.

Use a Car Cover

A reflective car cover can significantly reduce heat absorption, especially on dark-colored vehicles. These covers act like a sunshield for the entire car, reflecting sunlight away.

They’re especially useful for long-term parking or if you don’t have access to shade.

Ventilate Before Entering

Before you get in, open all the doors for 30–60 seconds to let the hot air escape. Then turn on the AC and set it to recirculate mode to cool the interior faster.

Some newer cars have remote start with climate control—use it to cool the car before you get in.

Install a Solar-Powered Ventilation Fan

These small fans attach to the window and use solar power to circulate air. They don’t cool the car dramatically, but they can help reduce heat buildup over time.

Choose Light Colors When Possible

If you’re buying a new car, consider lighter exterior and interior colors. White, silver, or beige cars reflect more sunlight and stay cooler than black or dark gray.

Light-colored seats and dashboards also absorb less heat, making the interior more comfortable.

Tips for Parents and Pet Owners

If you have kids or pets, extra precautions are essential.

For Parents

• Use a reminder system: Place your phone, purse, or left shoe in the back seat so you have to look there before leaving the car.
• Check the back seat: Make it a habit to open the back door every time you park—even if you think the car is empty.
• Lock the car when parked: Prevent children from climbing in and getting trapped.
• Teach kids about car safety: Explain why they should never play in or around parked cars.
• Call 911 immediately: If you see a child alone in a hot car, don’t wait. Call for help right away.

For Pet Owners

• Never leave pets unattended: Even “just a minute” can be deadly.
• Bring pets with you: If you can’t take your dog into a store, leave them at home.
• Use pet safety apps: Some apps send reminders if you leave your phone (and pet) in the car.
• Install a pet alert system: Devices like the Waggle Pet Monitor track temperature and send alerts if it gets too hot.
• Educate others: Share the risks with friends, family, and fellow pet owners.

Conclusion

So, how hot can a car get in the sun? The answer is: dangerously hot—even on mild days. Temperatures inside a parked car can soar past 120°F in under an hour, creating life-threatening conditions for children, pets, and even adults.

But knowledge is power. By understanding how heat builds up and taking simple preventive steps—like using a sunshade, parking in the shade, and never leaving loved ones unattended—you can protect yourself and others from harm.

Your car is more than just a vehicle. It’s a space where memories are made, errands are run, and lives are protected. Keep it cool, keep it safe, and enjoy the ride—responsibly.

Frequently Asked Questions

How hot can a car get on a 70°F day?

On a sunny 70°F day, a car’s interior can reach 110°F or higher within an hour. Dark interiors and direct sunlight accelerate heat buildup, making even mild days risky for children and pets.

Can cracking windows prevent a car from overheating?

Cracking windows helps slightly with airflow but does not significantly reduce interior temperature. It’s not enough to prevent dangerous heat levels—especially for children or pets.

How fast can a child overheat in a hot car?

A child’s body temperature can rise three to five times faster than an adult’s. Heatstroke can begin in as little as 10 minutes, even on relatively cool days.

Is it safe to leave a dog in a car with the AC on?

No. If the car is parked and the engine is off, the AC will eventually stop working. Even with the engine running, mechanical failures can occur, leaving the pet in danger.

Do sunshades really make a difference?

Yes. A quality windshield sunshade can reduce interior temperatures by up to 40°F by blocking direct sunlight from hitting the dashboard and seats.

Can heat damage a car’s electronics?

Yes. Prolonged exposure to high heat can cause car stereos, GPS units, and infotainment systems to overheat and malfunction, leading to costly repairs.