“Cracks can happen at anything below the freezing temperature, so 32 degrees Fahrenheit or zero degrees Celsius,” said Scott Bowe, a professor and wood products specialist at the University of Wisconsin-Madison.
Bowe clarified that the noises, known as frost cracks, are not caused by expanding sap.
“Some people have explained it as the sap is expanding like ice and causing the crack that actually is not what’s happening. It’s actually the drying of the wood that causes the crack to happen,” said Bowe.