An updraft is a current of air that moves upward, usually caused by warm air rising. When the sun heats the ground on a summer day, that warmth transfers to the air just above it. Since warm air is lighter than cool air, it rises, creating an updraft. Birds use updrafts brilliantly: hawks and eagles spread their wings and spiral upward on these invisible columns of rising air, soaring higher without flapping. Glider pilots do the same thing, riding updrafts to stay aloft for hours.

Updrafts also play a crucial role in weather. Inside thunderstorms, powerful updrafts can reach speeds of 100 miles per hour, lifting water droplets so high they freeze into hailstones. The stronger the updraft, the bigger the hail can grow before gravity finally pulls it down.

You've probably felt a gentle updraft if you've ever stood near a hot parking lot on a sunny day and noticed warm air rising past your face. The opposite of an updraft is a downdraft, where cool air sinks. Understanding updrafts helps explain everything from why storm clouds tower so high to how birds can glide for miles without beating their wings once.