Do you guys bring it to the beach or put your board in it for the car ride there so the heat doesn't screw it up during the ride because I put my board on the roof and I got in the car like 20 min later than drove to the beach and I got there and I had brown spots all over my board.
Shouldn't be much of a problem so long as you don't leave it in the sun for 20 minutes on the roof with the car not moving. Maybe try putting it in the boardbag inside and waiting untill right before you leave for the beach to strap it on the roof. Also, make sure you put the bag on the roof with the shiny/silver side up if your board bags like most of the ones I've seen with one side colored and the other a silver reflective material. I left my board/boardbag in a boat while camping at sebastian inlet once for a weekend that turned out to be flat and skimmed the whole time. Later the next week when we got some good swell back at home I got out onto the beach in the morning only to find my board impossible to pull out the bag from all the wax melted to the inside. It took me and some big hulky guy on the beach 15 minutes to wrestle my board out. It was some miracle i didn't rip the fin plugs out yanking on the fins/tail of the board.
I always take my board in a bag. I leave the bag in the car while surfing, then repackage the board before my exit. If I am going to surf all day, I usually do the same and just cover my board with towels. I don't trust leaving my bag on the beach.