Cold snap conjures the magic of frost

Frost flowers form in December 2010 at Stimpson Family Nature Reserve.
Frost flowers form in December 2010 at Stimpson Family Nature Reserve. The Bellingham Herald

On sharply cold and still nights, just the right weather conditions sometime combine to create magical crystalline shapes and coverings over windows, leaves, and bare tree limbs.

It’s a serendipitous convergence of physics and art in nature.

“It’s really amazing and so ephemeral. It’s gone by noon,” said Holly Roger of Wild Whatcom, a nonprofit outdoors-education organization.

Frost comes in many forms, from window frost to advection frost — which creates ice spikes on objects — and hoarfrost, which is a thin coating of ice crystals.

“Frost flowers” are ice extruded from a waterlogged object, such as a twig or branch. Rime technically isn’t frost, but rather a buildup or glaze of ice under cold, wet and sometimes windy conditions — like freezing fog that coats tree branches and power lines.

Hoarfrost, which is among the most common types, comes from an Old English word “hoar” or “hoary,” referring to something that shows the characteristics of old age, such as white or gray hair.

“Hoarfrost is like when an entire blade of grass is covered in frost,” Roger said.

She marvels at frost flowers, which look like thin, white threads or fluff, especially on a piece of wood.

“It looks like cotton candy or fiberglass,” she said. “It’s extruding the water. It has to be about freezing. It really, literally, is pulled into the air.”

Even more impressive than the beauty of frost flowers, Roger said, is the special conditions that allowed them to form.

“It’s (ice) coming from the wood, you have to have a significant amount of moisture in the weeks preceding, and then — cold.”

“It’s cold mornings that are mostly dry. It’s something about the cold air that does it. They’re just wonderful to touch because they just melt.”

If you want see hoarfrost, you’ll need a crisp, chill and dry morning when the temperature has dipped below freezing overnight and a fair amount of rain has fallen in the preceding days. Some good places to look include the trails around Padden Creek and Connelly Creek, Roger said.

Other good spots are in the Stimpson Family Nature Reserve east of Bellingham — especially on the section of trail along the beaver pond — and at Horseshoe Bend along the North Fork of the Nooksack River, east of Glacier.