"Frost quake" amid bitterly cold temps in SE WI, or sonic boom? National Weather Service says both possible

MILWAUKEE -- The bitterly cold temperatures may have caused a "frost quake" in southeastern Wisconsin on Tuesday night, January 12th. This, according to the National Weather Service in Milwaukee.

Officials with the National Weather Service in Milwaukee tweeted the following messages on Tuesday night:

Temperatures were in the single digits with sub-zero wind chills on Tuesday. A Wind Chill Advisory takes effect for Fond du Lac and Sheboygan counties at midnight Tuesday night/Wednesday morning.

The FOX6 Weather Experts said temperatures would drop below zero overnight, with wind chills staying below zero through Wednesday morning. Wind chills will stay in the -10 to -20 range overnight and into Wednesday.

So was what we heard and felt on Tuesday night a frost quake -- or a sonic boom?

FOX6's Vince Condella says we'll have to wait and see. The 115th Fighter Wing of the Air National Guard was conducting some night F-16 training at Truax Field in Madison -- which could have created a sonic boom.

Temperatures will warm up during the day Wednesday, warming into the 20s on Wednesday night.