Gas pressure is the atoms/molecules bouncing off something else. If the atoms have more energy, then they impart more energy into whatever they bounce off (insi

Gas pressure is the atoms/molecules bouncing off something else. If the atoms have more energy, then they impart more energy into whatever they bounce off (inside of the balloon), which essentially means higher pressure i.e. the balloon appears inflated again. Until the sun goes away and the OP's party dies for a time. :)