i recently too have had the burned "brims" of the lids on my guys. I had them sitting on a cement slab which got sun all day. I was told to move them off the cement since they will overheat from radiant heat. So now I have my collection about a foot off the ground in the lawn. I also will water overhead to cool the media off a bit when it gets blazing hot. Since the move there hasn't been any burning going on at all.