Car Interior Temperature Calculator
Find out how hot a car gets on a sunny day.
See the danger zone for children and pets left in parked cars at any outside temperature.
Why Cars Heat Up So Fast A parked car acts like a greenhouse. Solar radiation (sunlight) passes through glass easily — glass is largely transparent to the short wavelengths of visible and near-infrared light. Once that energy is absorbed by the dashboard, seats, and interior surfaces, it re-radiates as longer-wavelength infrared heat. Glass blocks that longer wavelength from escaping. The result: heat builds up inside with no way out.
Cracking Windows Does Almost Nothing This surprises most people. Research by the Stanford University School of Medicine and San Francisco State University confirmed that cracking windows 1–2 inches reduces interior temperature by only 2–3°F at most. The mechanism causing heat buildup — solar radiation through glass — is barely affected by a small gap. The only real solutions are shade, reflective windshield covers, or not leaving anyone inside.
The Numbers Are Alarming On a 70°F day, a car’s interior can reach 113°F in just 60 minutes. At 80°F outside, the interior hits 123°F within an hour. Most of the temperature rise happens in the first 20–30 minutes — a car can reach dangerously high temperatures even on a mild, cloudy day.
Children and Pets Are Especially Vulnerable A child’s body temperature rises 3–5 times faster than an adult’s. Children have a larger body surface area relative to their mass, and their thermoregulation system is less efficient. Heatstroke begins when core body temperature reaches 104°F. Death can occur when core temperature reaches 107°F. On average, a child’s body heats up 3–5× faster than an adult under the same conditions.
The Statistics More than 900 children have died in hot cars in the United States since 1998. The majority of these tragedies involve a parent or caregiver who forgot the child was in the vehicle — not intentional neglect. The “rear-facing, back seat” placement required for child safety seats means children are often out of the driver’s line of sight.
What to Do If you see a child or pet in a hot car showing signs of distress, call 911 immediately. In many US states, Good Samaritan laws protect people who break a window to rescue a child or pet in danger. Do not wait to locate the owner.