What’s the difference among freezing rain, sleet and hail?

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Dear Tom,

What’s the difference among freezing rain, sleet and hail?
— Margaret Chaet

Dear Margaret,

Hail and sleet both involve ice falling from the sky, but they are the result of entirely different atmospheric processes.

Hailstones form in vigorous thunderstorm updrafts. They start as tiny particles, but grow as they rise into the subfreezing portions of a cloud and collide with raindrops, eventually falling to earth. They can grow to grapefruit size or larger in severe thunderstorms.

Sleet (ice pellets) is a cold-season precipitation event that occurs when rain falls through a below-freezing layer. If this layer is thick enough, the raindrops freeze and fall to the ground in solid form as irregularly shaped ice pieces that bounce on contact with the ground.

Freezing rain is rain that produces a glaze when it freezes on contact with a below-freezing surface.