What causes rain?

This week’s weather question comes from Jeffrey Zerfas of Columbus, Georgia.

He wants to know: ‘What causes rain?’

As the sun heats the ground – it causes moisture in the ground to evaporate and rise. As the water vapor in the warm air rises, it cools and condenses into clouds.

These clouds (which have condensed out of the water vapor) are made of tons of tiny water droplets and ice crystals. In fact, the average size of a water droplet in a cloud is 1/2500th of an inch in diameter.

In order for it to rain, those droplets need to have a diameter of 1/125th of an inch or larger.

One reason droplets increase in size is by colliding with other droplets and ice crystals. It’s like one big dance in a storm cloud with all different shapes and sizes of dancers with different routines. Some droplets evaporate and condense on ice crystals while others continue to collide. Once those droplets get large enough – they become too heavy and fall to the ground.

If you have your own weather or science related question, email Meteorologist Carmen Rose at crose@wrbl.com


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