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If you hear a rumble in the distance this winter, it may not be the snow plow plodding along the road. It might actually be thunder.
While most of us consider the warmer months to have a monopoly on thunder and lightning, a thunderstorm can happen any time of year. “It’s really the same thing, just in a colder month,” says Mark Schnackenberg, chief meteorologist at KWWL in Waterloo.
For a storm to start brewing, there needs to be instability in the air surrounding the earth (the atmosphere). In the summer, that creates thunder, lightning, heavy rain — maybe even hail or tornadoes.
Come winter, thunderstorms focus on dumping truckloads of snow instead, potentially dropping up to two or three inches of snow in an hour. Unlike its springtime alter ego, though, a winter thunderstorm doesn’t have the energy to create high winds, hail or tornadoes.
But what about the lightning? It’s still there – it’s just that the lower clouds of winter make it harder to see in those grey skies. In fact, it can’t thunder at all without lightning.
“Lightning is a spark that heats the atmosphere quickly, then cools it quickly. That expansion of air creates thunder,” Schnackenberg says.
But thundersnow isn’t an everyday thing, which makes it all the more intriguing when it does start rumbling on a winter day. “It happens, on average, about one to three times a year,” Schackenberg says.
This article originally appeared in the "But Why?" section of the January/February 2011 issue of Iowa Outdoors magazine. Subscribe today or explore more of the magazine on Pinterest.