How fast a parked car heats up
A closed car parked in the sun works like a greenhouse: sunlight passes through the windows and heats the dashboard, seats and steering wheel, which warm the trapped air. Measurements published in the journal Pediatrics in 2005 by Catherine McLaren, Jan Null and James Quinn showed that the temperature inside rises fast even on mild days, with about 80% of the rise in the first 30 minutes. Cracking the windows made little difference.
Average temperature rise
| Time parked | Rise inside the car |
|---|---|
| 10 minutes | about 19 °F |
| 20 minutes | about 29 °F |
| 30 minutes | about 34 °F |
| 60 minutes | about 43 °F |
| 1 to 2 hours | about 45 to 50 °F |
The calculator interpolates these figures and adds them to the outside temperature. On an 80 °F day, the inside reaches about 99 °F after 10 minutes and 114 °F after 30 minutes. Dark cars, dark interiors and strong sunshine can heat up even more; shade and clouds slow the rise.
Why it is dangerous
Heatstroke begins when body temperature passes about 104 °F (40 °C), and a temperature of about 107 °F (41.7 °C) can be fatal. A young child’s body heats three to five times faster than an adult’s. In the United States, an average of about 37 children a year have died in hot cars since the late 1990s, most of them forgotten by a caregiver whose routine had changed. Dogs are also at risk, because they cool mainly by panting.
How to prevent it
- Never leave a child or a pet alone in a car, even for a minute and even with the windows open.
- Put something you need, such as a phone, bag or badge, on the back seat so that you check it every time.
- Lock the car when it is parked so children cannot climb in.
- Ask your child care provider to call you if your child does not arrive as expected.
If you see a child alone in a hot car, call 911 right away. Many states protect people who act to rescue a child in danger.