What are frost quakes and what’s the cause of the mysterious sound?

Residents in areas experiencing extreme cold may be startled by mysterious booming sounds and vibrations, a phenomenon meteorologists attribute to "frost quakes" or "cryoseisms.” These unusual noises occur when water rapidly freezes within the soil, causing it to expand and crack.

The process begins when rain or melted snow saturates the ground. As temperatures plummet quickly below freezing, this water solidifies and expands, building immense pressure on the surrounding earth. This pressure eventually causes the soil to fracture, resulting in loud booming sounds and slight tremors.

Evan Webb, a meteorologist with the National Weather Service in Louisville, Kentucky, confirmed that his office has received reports of these "loud booms" during periods of bitter cold. "I think some people initially wonder if it’s an exploding tree or something," he explained.

Webb noted that frost quakes are "relatively rare, especially in Kentucky… we don’t get quite cold enough very often to have saturated soil in the winter time to be able to freeze that quickly." He reassured the public that these events are "mostly harmless," adding that single-digit temperatures combined with wind chill pose a greater concern.

A social media post from the weather service office reiterated that while the noises can be startling, particularly at night, they are generally not a cause for alarm. "Those loud booms aren’t paranormal—they’re cryoseisms (Frost Quakes)!" the post clarified.

A massive winter storm left at least 30 people dead and tens of thousands without power.

Nearly 180 million people have been in the path of widespread heavy snow, sleet, and freezing rain in an area spanning the southern Rocky Mountains to New England in recent days, according to the National Weather Service.

Power line companies reported "catastrophic damage” in a number of states, warning that power restoration could take "weeks instead of days" for some customers.