Vehicle Heating Dynamics

The atmosphere and the windows of a car are relatively “transparent” to the sun’s shortwave radiation (yellow in figure below) and are warmed little. However this shortwave energy does heat objects that it strikes. For example, a dark dashboard, steering wheel or seat temperatures often are in the range of 180 to over 200 degrees F.

These objects (e.g., dashboard, steering wheel, childseat) heat the adjacent air by conduction and convection and also give off longwave radiation (red) which is very efficient at warming the air trapped inside a vehicle.

Objects Heated by the Sun Warm Vehicle's Air

  • 70 Degree Weather

  • 80 Degree Weather

  • 90 Degree Weather

Vehicle Heating Study

Studied temperature rise in enclosed cars on 16 dates between May 16 and Aug. 8, 2002.
(see graph of 16 case days)
Ambient temperature were between 72 and 96 degrees F
Dark Blue mid-size sedan with medium grey interior
Also tested with windows “cracked”
Published in Pediatrics 2005 (Click here to download)

“Cracking” the windows had little (i.e., < 3 deg.) effect • Vehicle interior color probably biggest factor