What are "exploding trees"? Here's what can really happen to trees in cold weather

Every time arctic air drops south, and temperatures plummet well below zero, social media lights up with a scary (and slightly cinematic) rumor called "exploding trees."

Videos circulate of loud, gunshot-like bangs ringing out in the forest, accompanied by captions warning that trees explode or blow off tree limbs. While the sounds are real and loud, the "explosion" narrative is a bit of an exaggeration.

Here is the science behind why trees go bang in the bitter cold, and why they are cracking, not combusting.

It's not an explosion, it's a frost crack

The technical term for this phenomenon is a frost crack.

While an explosion implies an outward burst of debris driven by combustion or massive internal pressure, what you are actually witnessing is a strong and sudden split.

If you inspect a tree after hearing one of these loud bangs, you won't find the tree blown into woodchips.

Instead, you will find a long, vertical fissure running up the trunk.

The science of expansion and contraction

Why does it happen? It comes down to a battle between the water inside the tree and the wood fibers trying to contain it.

1. Rapid Cooling: When temperatures drop aggressively fast (usually into the -20 range and especially colder), the outer layers of the tree bark and wood cool down and contract (shrink) much faster than the inner core of the tree.
2. Freezing Sap: Simultaneously, the sap inside the tree, which is essentially water and sugars, begins to freeze. We know from high school physics that when water freezes, it expands.
3. The Breaking Point: You now have outer layers trying to shrink tight against an inner core that is expanding. The tension builds immense pressure within the trunk.
4. The Snap: Eventually, the wood fibers can no longer withstand the tension. The tree snaps vertically to relieve the pressure.

Why is it so loud?

The loudness comes from the speed of the event. The tension builds slowly over hours of freezing, but the release happens in a millisecond.

That sudden release of massive potential energy creates a shockwave through the air, resulting in a deafening CRACK.

Does it kill the tree?

Usually not. While a frost crack looks painful, trees are resilient.

When the weather warms up, the wood expands, and the crack often closes. Over time, the tree will try to heal the wound. However, these trees are often scarred for life.

You may see trees with vertical ridges running up their trunks. These are often old frost cracks that have healed over, reopened in subsequent winters, and healed again.