The main function of the hypothalamus in temperature regulation is to maintain the body's homeostasis by detecting changes in body temperature and initiating appropriate physiological responses. It acts as a thermostat, triggering mechanisms such as sweating to cool the body or shivering to generate heat when temperatures drop. The hypothalamus integrates input from peripheral thermoreceptors and orchestrates responses through various systems, including the autonomic nervous system, to ensure optimal body temperature for metabolic processes.