Across parts of the world, winter has settled in hard. Sub-zero temperatures, sudden freezes, and heavy snow are affecting many regions, and with them an unexpected side effect: sharp cracking sounds echoing through parks, streets, and back gardens. Online, dramatic videos capturing the noise, some more intense than others, have spread quickly, often accompanied by warnings that trees are “exploding” in the cold. They are not. But they are reacting. Forestry experts say the sounds people are hearing are the result of a well-documented phenomenon known as frost cracking, dramatic, sometimes startling, and widely misunderstood.
What’s actually happening inside the tree
John Seiler, a professor and tree physiology specialist at Virginia Tech, told CNN that while winter weather can certainly damage trees, the viral framing has run ahead of the science. “They’re not actually exploding, at least not in the way the phrase suggests,” he said.When temperatures drop suddenly, trees do not always have time to acclimatise. Water and sap inside their tissues begin to freeze, and freezing water expands. That expansion creates internal stress, particularly when the outer layers of the tree cool faster than the inner wood. “That water expands as it freezes, and it can happen usually under very, very drastic drops in temperature,” said Doug Aubrey, a professor at the University of Georgia Warnell School of Forestry and Natural Resources. The effect is compounded by uneven contraction. According to the Wisconsin Department of Natural Resources, when temperatures fall quickly, the bark can shrink faster than the interior wood. The result is what the agency describes as “unequal contraction” between a tree’s outer and inner tissues. Bill McNee, a forest health specialist with the Wisconsin DNR, compared the process to ice expanding in a freezer. “When it does that, like ice cubes in your freezer, it expands very quickly,” he said. The resulting physical pressure, he explained, can cause the wood to split, producing the loud cracks people hear, and occasionally shedding branches.
Loud, dramatic, and usually harmless
The sound can be jarring. In some cases, frost cracks resemble a gunshot or sudden bang in the stillness of winter. While you definitely wouldn’t want to be nearby, documented effects are usually limited to frost cracks and tree branches falling off, while truly dramatic events, such as trees “exploding” in some viral videos, remain extremely rare. Some clips may even be AI-generated or staged for views, so it’s wise to take them with a grain of salt. Experts stress most frost cracks are harmless. “While frost cracks can be loud and cause branches to fall off, it would be extremely rare for a tree to fully explode because of it,” McNee said. More often, the split simply becomes part of the tree’s structure.Simon Peacock, an ISA-certified arborist with Green Drop Tree Care in Winnipeg, told CBC Canada that the cracks typically close once temperatures rise. “The break doesn’t harm the tree and will heal when the temperature warms up in the summer,” he said, though he noted that the same crack can reopen during future winters. Cases of serious damage, he added, are unusual. It is “extremely rare” to see the kind of destruction depicted in some social media posts, and many people never notice a frost crack at all unless they happen to hear it. “It’s going to be loud, but it’s not dangerous,” Peacock said. “Wood doesn’t go flying through the area.” For the tree itself, the split is not fatal, although damaged bark can allow insects, fungi or bacteria to enter.
Which trees are most vulnerable
Frost cracks tend to form along existing weak points. “These cracks tend to happen at a previous weak spot in the bark,” said Eric Otto, a forest health specialist at the Minnesota Department of Natural Resources, speaking to The New York Times. Thin-barked species, including maples, lindens and birches, are more susceptible, though frost cracking can occur across many species. Trees that are not native to a region may be at higher risk if they are not adapted to extreme cold. “Native trees can get frost cracks, but nonnative trees can be more susceptible if they are not adapted to the area,” Otto said. “I suspect that in areas that don’t typically have below-zero temperatures, those trees would also be more prone to frost cracks.”
Why most trees survive winter intact
Trees are not passive in winter. Many shed most of their internal water before cold sets in, entering a dehydrated, dormant state that helps them withstand freezing conditions. Their internal structure also offers redundancy. “A tree has thousands of vessels, or pipes,” Otto explained, “so if one bursts, the tree can continue to function.” Only in extreme cases, usually involving severe and rapid temperature swings, do frost cracks fail to heal and seriously compromise a tree’s health. For now, as winter deepens, experts say the unsettling noises are not a warning sign of catastrophe. They are simply the sound of living material responding to cold, dramatic, brief, and, in most cases, nothing to fear.
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