How quickly do hot cars become deadly?
“Children have died in cars with the temperature as low as 63 degrees. Basically the car becomes a greenhouse. At 70 degrees on a sunny day, after a half hour, the temperature inside a car is 104 degrees. After an hour, it can reach 113 degrees.”
– Jan Null, adjunct professor at San Francisco State University
When temperatures outside range from 80 degrees to 100 degrees, the temperature inside a car parked in direct sunlight can quickly climb to between 130 to 172.
In terms of heat-rise over time, it makes very little difference whether a car’s windows are closed or partially open. In both cases, a car’s interior temperature can rise approximately 40 degrees within one hour, even when the exterior temperature is only 72°F.
– American Academy of Pediatrics study (2005)
Animation shows how quickly interior temperature of car can rise in sunlight
This animation was developed by General Motors, to showcase how quickly the interior temperature of an enclosed car can rise to deadly levels:
Sources of scientific data on heat and cars
The following data is courtesy of Jan Null, CCM, Department of Earth & Climate Sciences, San Francisco State University.
How quickly does the interior temperature of a car rise, in direct sunlight?
- 10 minutes ~ 19 deg F
- 20 minutes ~ 29 deg F
- 30 minutes ~ 34 deg F
- 60 minutes ~ 43 deg F
Hull also notes that:
- “Cracking” the windows had little effect
- Vehicle interior color is probably the biggest factor in heat rise
Report by American Academy of Pediatrics on Heat Stress in Enclosed Vehicles
Abstract: Each year, children die from heat stroke after being left unattended in motor vehicles. In 2003, the total was 42, up from a national average of 29 for the past 5 years. Previous studies found that on days when ambient temperatures exceeded 86°F, the internal temperatures of the vehicle quickly reached 134 to 154°F. We were interested to know whether similarly high temperatures occurred on clear sunny days with more moderate temperatures. The objective of this study was to evaluate the degree of temperature rise and rate of rise in similar and lower ambient temperatures. In addition, we evaluated the effect of having windows “cracked” open.
Video from the Red Rover – My Dog Is Cool campaign:
From the British Columbia (Canada) SPCA: