Unexplained loud noises in Saint Louis: Experts point to rare weather phenomenon

Loud booms heard recently in multiple Saint Louis-region communities may have been caused by a sudden temperature drop, according to experts.

Rare weather phenomenon, called "frost quakes," likely were culprits for loud popping sounds heard in Franklin County and surrounding areas on Sunday.

A National Weather Service (NWS) St. Louis regional office meteorologist told The Delta Dunkin Democrat the NWS received multiple "frost quake" reports but does not track them.

The 30-plus degree temperature drop over the weekend in the Saint Louis region set the perfect conditions for a frost quake to occur.

"I don't know too much about frost quakes," says NWS meteorologist Jon Carney. "So, as water freezes, it expands.

"Freeze-quakes are sudden underground movements caused by freezing expansion of water within saturated soil and rock," he adds. "Basically, it's cold and the water in the ground expands and causes the ground to crack. We hear a rumbling sound when that happens, and sometimes we can feel it. We've had some reports from people telling us they've heard these loud noises, but I don't think we've heard any here on station."

Frost quakes are so weak that they do not register on the Richter scale, and the phenomenon is most likely to occur during extreme cold snaps, typically at night or in the early morning when temperatures are at their lowest, according to reports.

The last time the St. Louis region had confirmed frost quakes was more than a decade ago, and most frost quakes were heard on Feb. 2, 2014, when 40-degree temperatures dropped to single-digit readings by nightfall, reports stated.

Frost quakes that year also were reported in Canada, Indiana, Michigan, Ohio, and Wisconsin.