Originally posted by Tanzer In my sedan, if I know I am stopping somewhere in advance, I will put it in the trunk, under a blanket/towel for some added thermal insulation. I won't put the camera bag in the trunk once I get to my destination because I don't need the crooks to watch me moving my valuables. My trunk has an insulated lid and sides which definitely helps.
Sometimes I will put it on the rear floor of the passenger compartment, covered by one of those windshield sun reflectors, which definitely keeps the sun off the bag, and provides some amount of visual security too.
In either case, I've found that keeping the camera low in the car, in a padded camera bag, keeps the insides surprisingly cool.
If I am driving my van, it has some under-floor storage, which stays cool even longer.
I've done this plenty of times and the proof is in the temperature inside the bag. The thing you primarily want to keep cool is your lenses, those have some grease inside that you don't want to liquefy and spread over your aperture blades or onto the glass.
+1 exactly what Tanzer said.
The trunk stays much cooler than the inside of the car, and it's out of sight. I keep in under or wrapped in a small pile of jackets or towels, whether the temperature's hot or cold outside.
And if I need to move the camera and gear in and out of the trunk throughout the day, I try to remember to put it in the trunk as I'm leaving a location, not when I arrive at the next destination. That way no one has to notice if I have a bag full of gear in there; they may only see what I take out and take with me - which is often a camera plus one or two more lenses, kept in an ordinary, daypack-sized non-photo backpack.