You're sound asleep on a cold, wintry night, and all of a sudden a loud boom wakes you up. A few things on your shelves rattle for a second or two, then all is silent.
Was it an earthquake? Maybe, but the real culprit is likely a frost quake, a geological phenomenon brought on by winter weather. Unlike earthquakes, frost quakes are non-tectonic seismic events, meaning they are not caused by the shifting of the Earth's tectonic plates.
Also known as cryoseisms, frost quakes are caused by a sudden rapid freezing of ground and bedrock, usually when temperatures go from above freezing to below zero.
As moisture absorbed in the rock and soil freezes, it expands. This puts a great amount of stress on the areas around it.
Eventually, the stress is too much and the soil and rock will crack in an "explosive" manner, creating a loud sound and even shaking the ground surface.
Since temperatures are coldest in the overnight hours, most people experience frost quakes in the middle of the night, often waking up because of them.
According to the Maine Geological Survey, frost quakes can even leave cracks in the ground.
Cryoseisms are often very localized events, but multiple quakes can happen over a particular area. This may explain why people in multiple counties in Indiana felt frost quakes in the early morning hours of Feb. 10, as reported by WTHR in Indianapolis.
Early morning lows were below zero across the state, as cold as 18 degrees below at Frankfort Airport. The NWS reported that the temperatures on Feb. 10 were the coldest seen in the state since January 2009.
A tropical wave west of the Cape Verde Islands looks like it could be the next named tropical storm in the Atlantic Basin.
Following thunderstorms, cooler settles into the Midwest and Northeast through Midweek.
Cooler-than-normal temperatures are in store for Chicago this week.
One person is dead, and another remains critically injured after a lightning strike in Southern California.
Relief is on the way for portions of the Plains that are in the grips of the ongoing drought.
Southern CA (1991)
Torrid heat: 120 at Borrego Springs; 119 at Death Valley and Palm Springs.
Big Delta, AK (1992)
A rare tornado touched down; first since 1979 in Alaska.
Albuquerque, NM (1997)
A propane truck blew up after being struck by lightning. 3 people were injured.