Water returns to ground from clouds as rain, sleet, hail, or snow {precipitation, weather}|. Pressure changes and wind surges cause storms in tropics. Above tropics, fronts cause precipitation.
Yearly rainfall {rain}| averages 30 inches per year. Sea precipitation averages 44 inches per year. Land precipitation averages 26 inches per year. 25% goes into rivers, and 75% is on land.
When frozen raindrops pass through thunderstorm, they {hail}| pick up snow and ice.
When raindrops pass through very cold air, they {sleet}| can freeze.
If clouds are 0 C, snowflakes {snow, precipitation} form. Snowflakes have thin surface unfrozen-water film, which makes them stick to other snowflakes in special ways. That is why snowflakes are always hexagons. Snow can fall only above latitude 30 degrees. One foot of snow equals one inch of rain.
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Date Modified: 2022.0225