The sun is beating down on the concrete. it's a hot day, and you're in the house where it's conditioned. Your feet are fairly cool. When you step outside on the concrete the coldness in your feet seep into the concrete, and the heat from the concrete takes the cold away. It's like when a pot is on the stove, the pan transfers all it's cold to the hot, and the fire replaces the cold. Hope this helps!
