Tree-cracking cold: 39 below up north, 13 below in Twin Cities by Friday morning
Wind chill advisories continue until 9 a.m. Friday
The roof beams sent a loud boom through the Huttner Weather Lab Wednesday night.
Trees and wood expand and contract as temperatures change. Extreme cold can cause trees to crack, and the studs in your walls and roof to pop on cold arctic nights.
Paul Hetzler is an ISA-certified forester and a horticulture and natural resources educator for Cornell Cooperative Extension of St. Lawrence County in New York. He wrote this piece about the popping noises trees can make in subzero cold.
So what does happen when trees go ‘pop’ in the night (or day)?
As we all know, when water freezes, it expands. Luckily, sap is not pure water. It’s endowed with antifreeze in the form of sugars, and to a small extent, dissolved minerals.
There comes a point, however, when even sugar-fortified sap will freeze and expand. This may rupture the bark of a tree, resulting in an audible crack as well as a visible one. In many cases frost cracks close with no long-term ill effects, but sometimes they do become perennial.
Rapid temperature change: 50 degrees colder
Temperatures plunged 50 degrees in parts of Minnesota between Wednesday and Thursday morning.
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Here are some selected minimum air temperatures from around Minnesota Thursday morning.
Minneapolis-St.Paul International Airport: 11 below zero
Mankato, Minn.: 19 below zero
Redwood Falls, Minn: 21 below zero
Crane Lake, Minn.: 35 below zero
Ely, Minn.: 37 below zero
Lake Kabetogema, Minn.: 39 below zero
Coldest so far
Many Minnesota locations recorded the coldest temperature so far this winter season Thursday morning. The Twin Cities reading of minus 11 beat the minus-9-degree temperature recorded on Jan. 19.
Friday morning looks equally cold in some locations. I’m predicting temperatures will bottom out between minus 10 and minus 13 in the Twin Cities early Friday morning.
Temperature roller coaster ahead
The upper air pattern favors alternating Pacific and Arctic air mass swipes over the next week. That means highs in the 30s look likely Saturday, Monday and again next Thursday. In between temperatures chill into the 20s.
There is a chance for some snow Monday.
Stay tuned.