Sound needs a medium to propagate through and this medium which is moves through is the air. The colder the temperature is, the less excited (meaning kinetic energy) the air particles will be meaning that the sound wave will travel slower. In the sahara desert, since the temperatures are warmer, and more excited, the sound will propagate faster through the air.
*Note that sound waves rely on vibration to move and if the air is hotter the molecules in the air are vibrate more than compared to lower temperatures.
