DETROIT – Arctic air is pushing into Michigan, and wind chills could drop below -20 degrees this weekend.
When cold arrives fast like this, some people report sightings of “exploding trees.” Trees don’t actually blow up like fireworks, but they can split suddenly with a loud “bang.”
This is called a “frost crack.”
How can this happen? On a sunny winter day, the bark on a tree can warm up a lot, even when the air is still below freezing. Michigan State University Extension says bark temperatures can rise into the 70s under the right conditions.
When the sun sets (or the tree falls into shade), the outside bark cools and shrinks quickly. The wood inside the trunk cools more slowly. That mismatch can build stress until the trunk splits -- sometimes sounding like a gunshot.
Very low temperatures in Michigan have left some trees with long, vertical cracks that can run deep into the wood. Young trees with thin bark are more likely to crack, and the south or southwest side of the trunk is often the trouble spot because it warms the most in the sun.
The same crack can reopen in future winters, and it can become an entry point for decay and insects.
What should you do? The main danger is falling limbs, not the “bang” itself. If you hear a pop followed by a “whoosh,” a limb may have snapped and hit the ground.
During the coldest days, avoid standing or parking under large, old trees. After the cold snap, look for fresh splits or hanging branches and call a certified arborist if anything looks unsafe.
For young, thin-barked trees, a light-colored trunk wrap or burlap shade can reduce sudden warming -- just remove wraps in spring.