Why does it often seem warmer at 4:30 am than later in the morning?
Think of the atmosphere as being similar to your checking account-sunshine, and the heat it generates is like a deposit. The hours of darkness, and the loss of heat radiated from the ground back up through the atmosphere, is like a withdrawal. When the heat loss exceeds incoming heat from the sun, temperatures continue to cool...even after sunrise. Because the sun typically has to be above the horizon to generate more heat than is being lost to the atmosphere, the coldest temperatures on clear, windless days often don't occur until 30 minutes AFTER sunrise.