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.
On an 80-degree day
Studies show that temperatures rise in enclosed cars at the following average rate:
10 minutes ~ 19 deg F
20 minutes ~ 29 deg F
30 minutes ~ 34 deg F
60 minutes ~ 43 deg F
1 to 2 hours ~ 45-50 deg F
2 to 4 hours ~ 50-55 deg F
Two-thirds of the heating occurs in the first 20 minutes and “Cracking” the windows had little (i.e., < 3 deg.) effect on the heat. The vehicle interior color probably biggest factor.
This summer please keep your pets, your children and yourselves safe. If you feel symptoms of heat stroke such as: dizziness, disorientation, agitation, confusion, sluggishness, seizure, hot dry skin that is flushed but not sweaty, loss of consciousness, rapid heart beat, hallucinations, please seek help immediately.
Remember, “Children’s thermoregulatory systems are not as efficient as an adult’s and their body temperatures warm at a rate 3 to 5 times faster than an adult’s.” ~ Noheatstroke.org
According to the Heat Stress and Safety website, any person with signs or symptoms of heat stroke requires immediate hospitalization. However, first aid should be immediately administered. This includes removing the victim to a cool area, thoroughly soaking the clothing with water, and vigorously fanning the body to increase cooling. Further treatment at a medical facility should be directed to the continuation of the cooling process and the monitoring of complications which often accompany the heat stroke. Early recognition and treatment of heat stroke are the only means of preventing permanent brain damage or death.
Keep cool, keep hydrated and stay safe!