Here's why:

* Temperature and Kinetic Energy: Temperature is a measure of the average kinetic energy of particles. Kinetic energy is the energy of motion. So, hotter particles have more kinetic energy and move faster.

* Cold Air: In cold air, the particles have less kinetic energy and therefore move slower.

Think of it like this: Imagine a room full of people. If everyone is excited and moving around quickly, the room is "hot" (high energy). If everyone is calm and sitting still, the room is "cold" (low energy).

Let me know if you have any other questions!