The sounds people sometimes report during deep winter cold can come from the ground itself, meteorologists say. When water in soil rapidly freezes after temperatures fall below freezing, the freezing and expansion can create cracking and vibration that some residents hear as booming noises and feel as light shaking.
These noises are known as frost quakes or cryoseisms, a cold-weather phenomenon that occurs when rain or melted snow in the ground quickly freezes as temperatures rapidly drop. As the water turns to ice, it expands, and pressure builds around the surrounding soil, which can cause the ground to crack and make booming sounds along with small vibrations, meteorologists say.
Evan Webb, a meteorologist with the National Weather Service in Louisville, Kentucky, said the weather service office has received reports of “loud booms” associated with cryoseisms during bitter cold weather. Webb said some people initially wonder if they are “an exploding tree or something.”
Webb said frost quakes are “relatively rare, especially in Kentucky,” noting that the state does not “get quite cold enough very often” to have saturated soil in winter that can freeze quickly. He also said frost quakes are “mostly harmless,” while adding that single-digit temperatures with wind chill are a bigger concern.
The National Weather Service office said in a social media post that the noises can be startling, especially when they happen at night. The post described the sounds as cryoseisms rather than paranormal activity.