Older cars with cheaper dashboards would get cracks, they wouldn't melt. I have not heard of any problems in the 17 plus years I have lived here with any of the new cars. If you are worried about the sun, you can get a DASH Mat (dashboard cover) and a Sun Shade. Most people use the Sun Shade to help deflect the sun out of the car. It helps protect the interior from fading.

Bill

From the Valley of the Sun. -Phoenix, AZ