
Rain is the most common form of precipitation. When air rises and cools, water vapor condenses onto tiny dust particles or any surface it can find. This happens high in the sky where it is cold, so raindrops usually start as ice crystals. When the drops or crystals grow large, they fall from the clouds. If the air is warm, then it rains. Rain mostly comes from cumulus clouds. Surprisingly, falling raindrops are not really shaped like teardrops. They tend to be round and flatten out into the shape of squished buns as they fall. This misconception may arise from seeing tear-shaped drops streaking down a window.
Meteorologists categorize rain as light with scattered drops falling at 0.1” (2.5mm) per hour, moderate with rain falling at 0.3” (7.5mm) per hour or heavy at over 0.3” per hour. Drizzle falls slowly with tiny drops of less than 0.02” (0.5mm). About 700 drizzle drops equal the size of one raindrop. Warmer air can hold more moisture, so due to climate change, many places will likely experience more raindrops and more extreme weather.