Another round of snow — including reports of thundersnow — blanketed the summits of Mauna Kea and Mauna Loa on the Big Island of Hawaii on Sunday and Monday. Mauna Kea park rangers reported “significant snowfall with continuous thunder and lightning over the summits,” the National Weather Service in Honolulu tweeted late Sunday.

Upward motion of air (which meteorologists call convection) helps produce thunderstorms. But it’s fairly rare to have convection within a winter storm. Thunder and lightning are much more common in warm-season thunderstorms, according to meteorologist Jeff Haby. When there’s strong enough convection, along with plenty of moisture available, a winter storm can produce thundersnow. READ MORE