A major winter storm slamming much of the Northeast is creating something called "thundersleet."
The unusual weather phenomenon has been reported in Virginia and is now heading to the Washington D.C. area, according to a Facebook status posted by the Virginia Weather Network.
Thundersleet is exactly what it sounds like. It happens when thunder and lightning occur at the same time as sleet or freezing rain. The mash-up of weather events is extremely rare, according to a 2009 article from Scientific American which notes that "less than 1 percent of observed snowstorms unleash thundersnow, according to a 1971 NSW study."