Clouds act as a blanket at night by trapping heat radiated from the Earth's surface. Here's how it works:

* During the day: The sun warms the Earth's surface.

* At night: The Earth cools down and radiates heat back into the atmosphere.

* Clouds act as a barrier: Clouds are made of water droplets or ice crystals. These particles absorb some of the infrared radiation (heat) emitted from the Earth. This trapped heat prevents the Earth from cooling down as quickly as it would if there were no clouds.

Think of it like this: a blanket on your bed traps your body heat, keeping you warm. Clouds act similarly, trapping the Earth's heat and preventing it from escaping into space.

This is why nights with cloudy skies tend to be warmer than nights with clear skies.