Question

why in the desert during the day the temperature is very hot and during the night the temperature is very cold?

Answer 1

The desert becomes hot during the day and cold in the night because deserts have extremely low humidity. Water vapour in the atmosphere acts to trap long wave infrared radiation from the ground, and dry desert air is incapable of blocking sunlight during the day (due to absence of clouds) or trapping heat during the night. Thus, during daylight most of the sun's heat reaches the ground, and as soon as the sun sets the desert cools quickly by radiating its heat into space.