12 Feb
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Thunder Snow

At its most intense, last Thursday’s snow storm was piling on flakes at a rate of two inches an hour. In those whiteout conditions, many people online began to report hearing a strange sound. Some initially thought it was snow plows rumbling through the neighborhood. A few reported flashes of light, and wondered whether those might have been electrical lines blowing. Neither of those occurrences would have been unusual for this time of year. The cause of the disturbances, though was much more unusual: thunder snow.

Summer thunderstorms usually happen on those sultry days when the air is warm and humid. A dry, much colder air mass moves in on top of the humid one. Because hot air rises, it begins to be pulled through the cold, dry mass at a rapid rate. When that happens, the molecules rub against one another, building static electricity. Periodically, the charged molecules are released in large bolts.

According to an article from the University of Wisconsin, “Static charges form in a storm composed of ice crystals and liquid water drops. Turbulent winds inside the storm cause particles to rub against one another, causing electrons to be stripped off, making the particles either negatively or positively charged… Eventually a lightning bolt happens to neutralize the electric field.

“The lightning bolt rapidly heats the air around it, to as hot as 50,000 degrees. This rapid warming causes the air to quickly expand and generate a sound wave. That sound wave is thunder. Sound can interact with objects in multiple ways. Snowfall, and snow on the ground, tends to muffle the sound.”

For a phenomenon like this to happen in winter is much less frequent than in summer. According to a Penn State article, thunder snow is recorded in less than one per cent of snowstorms. One of the reasons is that the shape of storms in summer is different. The warmer air may rise to frigid, dry air for 40,000 feet or more, providing plenty of opportunity for the buildup of static electricity to happen as it rises. In winter, most storms brew at roughly 20,000 feet and the turbulence caused by air movement is weaker.

The thunder we experienced back on the ninth was a product of the storm swinging out over the ocean as it approached. Since the air over the ocean is typically warmer than the land in winter, the mass was warmed and then collided with the cold, dry air that we were experiencing. That collision of air masses caused the friction that would build in the clouds and eventually discharge as thunder and lightning.

Although thunder snow is not particularly dangerous in and of itself (being struck by snow lightning is far rarer than during a summer storm), it is a signal that the weather is going to deteriorate extremely rapidly. A University of Missouri professor’s research indicates that there is an 86% chance that the snow will fall at eight inches per hour in the time surrounding thunder snow. If there were any doubt about seeking shelter, thunder snow should be the final warning that things are about to go bad in a matter of minutes.

Thus, although late winter storms may be a bit disappointing for those of us searching for crocuses peeking through the mud as a sign of spring, take comfort in the fact that we have witnessed an event that is far less expected than flowers near Valentine’s Day.


  • Thanks for the explanation! The storm – and the under and lightening within- was quite aggressive on Thursday. Cool to know the how and why!

  • Thanks for taking the time to write, Meg! Yes, the storm was pretty impressive as it was, but the thunder snow was a first for me!

  • That was great! Showed it to my kids..pretty cool!

    • Glad you liked it! It was a pretty fascinating event, and I enjoyed writing about it. Thanks for writing!

  • As always, a great read! Thanks

    • Thanks, Nisa! Glad you liked it!

  • Awesome read! Never realized there was such a thing as Thunder Snow!

    • Thanks, Charlene! It was a rare event, and I feel lucky to have witnessed it!

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