Temperature differences on the feet can have a wide variety of causes. There are scientific studies that have recognized certain developments in this regard; People who have such temperature differences on their feet can suffer from polyneuropathy, for example. This is often just referred to as PNP. Patients with polyneuropathy suffer from damage to the peripheral nervous system, i.e. the nervous system outside the spinal cord and brain. Type 2 diabetes mellitus is often a cause. You can find out more about this here !