What causes freezing rain and sleet?

March 12, 2008 1:29:05 PM PDT
Freezing rain and sleet both originate from winter storms, but they have very different reasons for their occurrence!

Erica's Answer:

Freezing rain falls through the low levels of the atmosphere as liquid rain. But the rain touches surfaces (such as grass, tree branches, or roads) that are colder than the freezing point of water. These surfaces cool the rainwater down to its freezing point, which is why freezing rain looks like a coating of ice.

Sleet pellets also start out as raindrops, but as the raindrops fall toward Earth's surface, they enter a cold layer of below-freezing air. These raindrops freeze before they reach ground level, which is why they look like tiny balls of ice.

If you want to figure out whether sleet or freezing rain will fall in a particular storm, you must know how thick the layer of below-freezing air is going to be. If the cold layer is only a couple hundred feet, you will most likely get freezing rain, but if the cold layer is deeper, you will get sleet. It is also possible to get a combination of sleet and freezing rain.

- Erica


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