<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/IceBalls1.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/IceBalls1.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/IceBalls1.jpg?v=ap&w=980&h=551 800w" > Lake Michigan Ice Balls Thousands of ice balls washed up at Holland State Park in Holland, Michigan, on Friday, Feb. 14, 2020. (Holland State Park/Michigan Department of Natural Resources)

At a Glance The ice balls need lake-effect snow, cold temperatures and waves to form.

Thousands washed up Friday at Holland State Park in Michigan.

They ranged from the size of softballs to the size of yoga balls.

The elements aligned over the past several days to create not one, but two, rare weather phenomena on the shores of Lake Michigan.

On Monday, weather.com meteorologist Brian Donegan told us about a pair of ice volcanoes erupting at Oval Beach in Saugatuck, Michigan. They occur when waves cause an increase in pressure on the lake's ice sheet, and water punches a hole in the ice, Donegan explained.

Two days earlier and eight miles to the north, thousands of ice balls washed up at Holland State Park in Holland, Michigan.

(MORE: Ice Volcanoes Erupted on a Michigan Beach Sunday)

"We went down to the beach to check on things and we saw these large ice balls ," Sean Mulligan, a supervisor at the park, told the Detroit Free Press. "I had heard of them before, but I hadn't ever seen them."

Mulligan shared photos of the ice balls on the park's Facebook page .

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/IceBalls2.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/IceBalls2.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/IceBalls2.jpg?v=ap&w=980&h=551 800w" > A park supervisor said the ice balls that washed up at Holland State Park in Holland, Michigan, on Friday, Feb. 14, 2020, ranged from the size of softballs to yoga balls. (Holland State Park/Michigan Department of Natural Resources)

The National Weather Service office in Grand Rapids, Michigan, also wrote about the balls on its Facebook page .

"Well, it took a while, but it finally got cold enough for ice balls to form on Lake Michigan this winter," the post said.

Ice balls can usually be seen in late December and early January when temperatures fall into the teens and single digits, the post said. Cold temperatures cause heavy lake-effect snow to form a layer of floating slush on the lake, the NWS office explained. Wave action sculpts the slush into spheres.

"These balls of ice then wash up on the beach by the thousands and freeze solid," the post said.

(WATCH: Meteorologist Ari Sarsalari Explains Ice Balls)

Mulligan told the Free Press the ice balls varied in size from softballs to yoga balls.

A blast of arctic air sent temperatures plummeting late last week in the Upper Midwest. The low dropped to 6 degrees Friday in Holland, Michigan, and wind gusts up to 19 mph were recorded.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.