Where Does Rain Come From?
Rain comes from clouds. There is always some moisture in the air. It evaporates from lakes and oceans. The water floats in the air as invisible vapor until the air cools. When the air cools, some of the water vapor condenses into tiny droplets of water. The droplets collect to form the clouds we see in the sky. These clouds darken to rain clouds as they come to contain more moisture.
If the air continues to cool, the cloud droplets join together and form big drops. When the drops become too heavy to float in the cloud, they fall to earth as rain. Rain happens in two ways usually: as a drizzle or a shower. A drizzle is a slow, light rain that can go on for hours. A shower is a fast, heavy rain that lasts just a short while.
Raindrops fall at a speed of 7 to 18 mph. In wind, they might fall much faster. Flash floods happen when it rains a lot and water rises very quickly. Weather reporters use Doppler radar to detect rain, hail and other storms. This equipment can tell how much moisture is probably coming, as well as the wind speed. Rain contains more than just water. It might contain dirt, dust, insects, grass or even chemicals.