The majority of the United States is bracing itself for a potentially historic polar vortex winter storm this weekend. The lower 48 states could experience average temperatures of 11 to 12 degrees Fahrenheit, while those in the North and Midwest will likely see that number drop to -25 degrees or low er. But aside from the bitter subzero temperatures, mountains of snow, and damaging ice, some news and social media posts are warning of a completely different kind of problem. “EXPLODING TREES are possible in the Midwest and Northern Plains on Friday and Saturday, as temperatures are forecasted to fall 20 degrees BELOW zero!” Max Velocity, a popular meteorology account, cautioned his over 262,000 Facebook followers on January 20. Another widely syndicated news article proclaimed,“Meteorologists warn that temperatures falling 20 degrees below zero could cause trees to split suddenly, posing risks to people, homes, vehicles, and power lines across North Dakota, South Dakota, Minnesota, Wisconsin, Iowa, and Michigan.”  Although the “exploding tree” phenomenon is a real thing, the underlying physics isn’t as worrisome as it sounds. But to understand this relatively common occurrence, it’s far more crucial (and potentially lifesaving) to know about the climate that causes trees to rupture. What is a polar vortex? The winter deluge set to inundate as many as 230 million people in the U.S. this weekend is only possible through a combination of both the polar vortex and the ongoing climate crisis. Although the vortex usually only makes headlines as it bears down on the country, it’s actually one of the two air formations constantly swirling above the planet’s polar regions.  In the Northern Hemisphere, the polar vortex remains above the Arctic for most of the year, but occasionally stretches further south after interacting with an unusually warm upper atmosphere. Combine that with moisture from California and the Gulf of Mexico, and you get a mass of bitterly cold air, heavy snowfall, and life-threatening conditions.  The opposite happens in the Southern Hemisphere, when the polar vortex around Antarctica creeps northward. However, the southern Antarctic polar vortex outbreaks do not typically reach as many populated areas as the northern Arctic polar vortex does. If it feels like polar vortex storms are occurring more often than in the past, you’re probably onto something. Multiple studies show a clear increase in linked weather events, many fueled by rapidly warming Arctic temperatures. That certainly seems to be the case right now.According to the National Snow and Ice Data Center, Arctic sea ice is currently at an all-time low for this time of year. A polar vortex outbreak can quickly turn deadly once it arrives. Anyone without proper protection from the freezing temperatures could start to see the beginning stages of hypothermia within an hour of direct exposure. Downed power lines, automobile accidents, and delayed first responders only add to the dangers, while temperatures often remain below freezing long after the weather subsides. Read more about weather preparedness The safest ways to stay warm during a power outage How to prepare your home for winter Prepping isn’t just for preppers anymore—it’s time to get a go-bag Homes at risk of climate disasters are often unprepared Can trees really explode? Although many people on the internet are warning about exploding trees, it’s not exactly worth the worry. That’s not to say they don’t happen. Naturalists have described similar experiences for centuries—but few (if any) cite their deadly consequences, and they’re definitely not as dramatic as they literally sound. “In the great frost in 1683, the trunks of oak, ash, walnut, and other trees, were miserably split and cleft, so that they might be seen through, and the cracks often attended with dreadful noises like the explosion of fire-arms,” wrote 18th-century Scottish botanist John Claudius Loudon in his Encyclopaedia of Gardening. “In the frost of 1837–8 large bushes of heath had their stems split by the frost into shreds, and the wood of the evergreen oak and that of the sweet bay was cracked and split in a similar manner.” Some Indigenous cultures are so familiar with the occurrences that they use them to mark their lunar calendar cycles. For example, the Lakota people of the Dakotas designate one winter period as Cannápopa Wi, the “Moon When Trees Crack From The Cold.” Trees explode—or, more accurately crack—similarly to how you lost a favorite water bottle after leaving it in the freezer for too long. Once temperatures dip below 32 degrees, the sap inside certain trees begins to solidify and expand. If it is particularly frigid, around -20 degrees or lower,the outside bark shrinks faster than the bark on the inside. Eventually, the stress wins out and causes the exterior to snap, producing a loud “bang” in the process. “This is most likely to happen on clear, calm nights, especially late night into early morning when temperatures fall quickly,” meteorologist Shawn Cable explained. “It can happen to a lot of different types of trees, but some common ones around here include maples, ash, apple or crabapple, poplar or cottonwood, and willow, along with younger trees that haven’t yet developed thicker bark.” The damage is occasionally harmful to the tree itself, but even then, it’s often able to continue growing once the spring thaw arrives. In any case, exploding trees aren’t something to avoid—but the polar vortex that can cause it certainly is. How to stay safe in extreme cold To prepare ahead of extreme cold, the National Weather Service recommends following updated forecasts and adjusting plans accordingly to avoid being stranded in the cold. If driving, also make sure that your car has at least a half a tank of gas so that you can stay warm if you become stranded and be sure your winter car kit is updated.  The colder it is, the more protective clothing you need to wear. Credit: National Weather Service Limit time outside whenever possible during extreme cold. If you need to venture outside, wear layers of warm clothing (and sunscreen) and watch for signs of frostbite and hypothermia. Frostbite can set in in 30 minutes or less when the wind chill is -15 degrees or lower.  Also, be extremely careful when operating a generator due to a power outage. Improper use can result in carbon monoxide poisoning and other dangers. If power does go out, follow these tips to help keep you and your family warm safe. In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. 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