Why Car Interiors Get So Hot in Summer

Weve all heard the saying, If you cant take the heat, get out of the kitchen. But during summer, you could insert the word car  into that sentence just as easily. Why is it that your car feels like an oven, no matter if you park in the sun or shade? Blame the greenhouse effect.   A Mini Greenhouse Effect Yes, the same greenhouse effect that traps heat in the atmosphere and keeps our planet at a comfy temperature for us to live is also responsible for baking your car on warm days.  Your cars windshield not only allows you an unobstructed wide view while on the road, it also allows the sunlight an unobstructed pathway inside your cars interior. Just like , the suns shortwave radiation passes through a cars windows. These windows are only warmed a little, but the darker colored objects that the sunrays strike (like the dashboard, steering wheel, and seats) are heated immensely due to their lower albedo. These heated objects, in turn, heat the surrounding air by convection and conduction. According to a 2002 San Jose University study, temperatures in enclosed cars with a basic gray interior rise approximately 19 degrees F in 10 minutes time; 29 degrees in 20 minutes time; 34 degrees in half an hour; 43 degrees in 1 hour; and 50-55 degrees over a period of 2-4 hours.   The following table gives an idea of just how much above the outside air temperature ( °F)  your cars interior can heat up over certain periods of time.   Time Elapsed 70 F 75F 80F 85F 90F 95F 100F 10 minutes 89 94 99 104 109 114 119 20 minutes 99 104 109 114 119 124 129 30 minutes 104 109 114 119 124 129 134 40 minutes 108 113 118 123 128 133 138 60 minutes 111 118 123 128 133 138 143 1 hour 115 120 125 130 135 140 145 As you can see, even on a mild 75 degree day, the inside of  your car would warm to triple digit temperatures in just 20 minutes!  Ã‚   The table also reveals another eye-opening reality: that two-thirds of the temperature spike happens within the first 20 minutes! This is why drivers are urged not to leave children, the elderly, or pets in a parked car for any amount of time -- no matter how seemingly short -- because contrary to what youd think, the bulk of the temperature rise happens within those first few minutes.   Why Cracking the Windows is Useless If you think you can avoid the dangers of a hot car by cracking its windows, think again. According to the same San Jose University study, temperatures inside a car with its windows cracked down rise at a rate of 3.1  °F every 5 minutes, compared to 3.4  °F for closed windows. The   just isnt enough to significantly offset the .    Sunshades Offer Some Cooling Sunshades (shades that fit inside the windshield) are actually a better cooling method than cracking windows. They can reduce your cars temperature by as much as 15 degrees. For even more cooling action, spring for the  foil type since these actually reflect the suns heat back through the glass and away from the car. Why Hot Cars are a Hazard A stifling hot car isnt only uncomfortable, its also dangerous to your health. Just like overexposure to high air temperatures can cause heat illness such as heatstroke and hyperthermia, so can   but even faster since because they. this leads to hyperthermia and possibly death. Young children and infants, the elderly, and pets are most susceptible to heat illness because their bodies are less skilled at regulating temperature. (A childs body temperature warms 3 to 5 times faster than an adults.) Resources and links: NWS Heat Vehicle Safety: Children, Pets, and Seniors.   Heatstroke Deaths of Children in Vehicles. http://www.noheatstroke.org McLaren, Null, Quinn. Heat Stress from Enclosed Vehicles: Moderate Ambient Temperatures Cause Significant Temperature Rise in Enclosed Vehicles. Pediatrics Vol. 116 No. 1. July 2005.