It depends on the heat,if its in the 90's and the sun is hitting the concrete it will likely get too hot to walk on.In 2010 I went to Aquatica in August in what was almost certainly the hottest day of the year,the weather channel said 97 degrees,the thermometer at the wave pool said 100 all day and when I got back to my car the thermometer had the outside temperature at 105,the highest I've ever seen it hit.Up until that day I had always done the water parks barefoot and at certain times the ground did get hot,I would run away from that spot where the sun was hitting constantly but it wasn't burning hot throughout the park,this was of course with normal summer heat, 88-93,It got hot by spots but I tolerated it.Now let's get back to that day in Aquatica,by 10:30-11am the floor started getting hot,eventually I walked by a restaurant with a shaded floor but when I walked away from it with the sun hitting the floor I automatically knew this was the hottest I had ever tried to walk on and I had to get back on the shadow of the building.At that point I knew I had to go find some flip flops in a store or I wouldn't be able to continue on.It took me about 5 minutes to get the courage to walk into the ground that must have been like 130 degrees,went back to the locker to get some money to buy the flip flops at a store,since that day I always bring the flip flops or some other water shoe.