A freeze-thaw cycle (FTC) occurs when air temperature drops low enough to freeze water (32°F), and then increases enough for it to thaw again. FTCs usually occur most frequently in the wintertime, though have the potential to occur at any time of year.Mechanical weathering includes processes such as water in cracks freezing and expanding, or changes in temperature that expands and shrinks individual minerals enough to break them apart. Freeze-thaw weathering occurs when rocks are porous or permeable. It is an example of Mechanical Weathering. Water enters different cracks in the rock. When the temperature drops below freezing the water inside freezes and expands.