how hot can it get in a parked car

[MacAyla]

The temperature inside a parked car can become lethally hot, far exceeding the outside temperature. On a typical sunny day, even if it's only 70°F (21°C) outside, the interior of a car can reach 115°F (46°C) within 60 minutes. The critical finding from studies is that the majority of this temperature rise, about 80% of the increase, happens within the first 30 minutes. This rapid heating effect makes a car a deadly environment for children, pets, or anyone left inside, regardless of whether the windows are cracked open.

This phenomenon, often called the "greenhouse effect," occurs because sunlight enters through the windows, heating the dashboard, seats, and interior surfaces. These surfaces then radiate heat, which is trapped inside the car. The enclosed space prevents the hot air from escaping effectively. Cracking the windows open has been proven to have a negligible effect on slowing this temperature climb.

The following data, based on research from the Department of Earth Sciences at San Francisco State University, illustrates how quickly temperatures can soar:

Elapsed Time (Minutes)	Outside Air Temperature (°F)	Internal Car Temperature (°F)
0	70	70
10	70	89
20	70	99
30	70	104
40	70	108
50	70	111
60	70	115

It is a dangerous misconception to think a quick errand is safe. Hyperthermia (heatstroke) can occur when the body temperature exceeds 104°F (40°C). A child's body temperature rises three to five times faster than an adult's. There is no safe amount of time to leave a child or pet in a parked car, even with the air conditioning running previously or the windows partially down. Always check the back seat and make it a habit to never leave a living thing in a vehicle unattended.

[OCaleb]

It gets dangerously hot, incredibly fast. I made the mistake of thinking "just five minutes" was okay. I came back to a car that felt like an oven. The steering wheel was too hot to touch, and the air was thick and heavy. That five-minute errand was a wake-up call. It’s not an exaggeration; it’s a real and immediate danger. Never risk it.

[McAnastasia]

Think of your car's interior as a solar oven. The sun's energy passes through the glass and gets absorbed by the seats and dashboard. They then re-radiate that heat, but the windows trap it inside. This is the greenhouse effect in action. On an 85-degree day, the temperature inside can hit a scorching 120 degrees in under half an hour. Cracking the windows does almost nothing to stop this rapid heat buildup.

[DiJaxon]

The best approach is prevention. Always use a sunshade for your windshield; it reflects a significant amount of heat. If possible, park in the shade, though remember the sun moves. Tinted windows can also help. Most importantly, never, under any circumstances, leave a child, pet, or vulnerable adult in a parked car. To cool it down quickly before driving, open all the doors for a minute to let the super-heated air escape before turning on the A/C.