It's HOT and SUNNY where I live.
I find that if I put up a reflective shade in my windshield when I park the car, it still sometimes gets hot inside, but it's always bearable. If I don't put one up, the car sometimes gets as hot as an oven and I just can't get in until it clears out a little. I now use one religiously, ANY time that I park the car and know it will or might be exposed to sunlight.
I know some people also uses nonreflective cardboard sunshades.
I want to know, how many of you use them?