Weeks of sub-zero cold create rare ‘ice wave’ atop East Coast mountain, photos show

Temperatures as low as 16 below zero have created what amounts to a frozen ocean wave on Mount Washington, the New Hampshire mountain peak known for notorious weather extremes.

The formation looks exactly like something you’d see breaking off Maui, but made of solid ice, photos show.

It’s dangling over the roof of the Mount Washington Observatory.

“After several days of icing conditions, the summit had unique rime ice formations everywhere, so weather observers took this opportunity to go subarctic surfing!” the observatory reported in a Dec. 10 Facebook post.

“The rime ice wave on the top of our tower hasn’t formed in nearly two years, so it is rare to see it as big as it is in these photos.”

Daytime temperatures on Mount Washington have been at zero or below for much of December, according to AccuWeather. A monthly high of 10 degrees was forecast for Wednesday, Dec. 11.

The 6,286-foot peak is frequently surrounded by clouds, which is necessary for the rime ice phenomenon to occur, experts say.

“Basically, the cloud (fog) is made up of millions of water droplets.. ... All these droplets need in order to turn into ice is something to come into contact with that is below freezing,” the observatory says.

“This impact essentially causes the supercooled water droplet to turn into ice, and as the droplets continue to impact the structure, the ice builds up into the direction of the wind.”

Mount Washington’s extreme temperatures have resulted in up to 9 inches of rime ice forming in a single hour, the observatory says.

This story was originally published December 11, 2024 at 8:52 AM with the headline "Weeks of sub-zero cold create rare ‘ice wave’ atop East Coast mountain, photos show."