Why Do Trees Make That Rattling Sound at Night?

Have you ever heard trees click or rattle when the house is quiet at night? It is not ghosts! It is water moving inside the tree. Trees have tiny straws called xylem that pull water from the ground to their leaves. During the day, the sun gets hot, and the leaves lose water like sweat. This pulls on the water straw tightly. At night, when it cools down, the pressure changes slightly. The water stretches and snaps back inside these tiny tubes. This makes a small popping or rattling sound. It is like the sound of ice cubes cracking in a glass or water pipes settling after you turn off the faucet. Even though trees do not have ears to hear, they make this noise all by themselves as they adjust their internal water levels overnight.