This specific process (the freeze-thaw cycle) is called frost weathering or cry fracturing. Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Thermal stress weathering results from the expansion and contraction of rock due to temperature changes. Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand and contract. As this happens over and over again, the structure of the rock weakens. Over time, it crumbles. Chemical weathering occurs only in hot climates, and mechanical weathering occurs only in cold climates. Chemical weathering happens in place, while mechanical weathering involves the transport of rocks.