I thought I heard thunder during a snowstorm. Is that possible?
Yes. A storm that includes any occurrence of thunder with snow is called a thundersnow event or thunder snowstorm. Lightning and thunder go together; you can’t have one without the other. Thunder is generated when the lightning heats the air five times as hot as the sun, which causes the air to rapidly expand and generate a sound wave.
There is much we don’t know about lightning but we do know that it requires both ice crystals and liquid water in a cloud with strong updrafts. Since winter storms usually have mostly ice crystals, thunder is uncommon in winter storms. And not only is thundersnow rare, it is also hard to hear, as the accompanying snowfall acts as an acoustic suppressor, or sound absorber.
Between 1961 and 1990, there were only 191 reports of thunder snowstorms, and less than six official observations of thundersnow within southern Wisconsin. Madison’s most memorable thundersnow event occurred at 5:09 PM January 26, 1996, when lightning produced an eerie purple sky. States with the best chance of thundersnow are eastern Nevada and Utah, followed by the Central Plains and Great Lakes states.