San Bernardino Mountains got a nice layer of frosting Saturday morning. It's called graupel

It's been thankfully cool this week, a big relief after the record heat wave earlier in the month. It was so cool last night that the San Bernardino Mountains saw a nice little layer of frosting this morning.

It's not snow, nor is it hail.

"It's called graupel," said Philip Gonsalves, a meteorologist with the National Weather Service.

Again, graupel (pronouncer: GRAH-pul).

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Gonsalves says it was caused by unusually low temperatures and thunderstorms up in the mountains last night. "Some of the precipitation that fell out of the thunderstorm fell as grapple. There was also some small hail mixed in with it," he said.

How we know it's graupel vs. hail

From left to right: hail, graupel, sleet, snow

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Courtesy NWS

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Many people confuse the two — but not if you know about the crush test.

"The easiest way to distinguish between graupel and hail, because they look similar, is that graupel you can crush relatively easily," Gonsalves said. "Hail, you really can't crush easily."

That's due to different processes from which the two are formed.

Hail is created in layers, Gonsalves said.

"There's layers of ice upon layers of ice, and that makes it difficult to crush," Gonsalves said.

While graupel feels kind of like a really precious hard-shelled ice cream treat on a hot summer day.

"Grapple is just a droplet of water [where] the outside of which got super cooled. So it froze, So it's like frozen on the outside, but liquid on the inside."

Will it last?

Gonsalves says these little delicate weather concoctions, which dusted the mountains at above 7,000 ft in elevation, will melt off pretty quickly — especially by the time the temperature picks back up on Sunday, with highs expected in the mid to high 80s.

For a more in-depth explainer on the science behind graupel, here's the National Weather Service itself.