One of the most common temperature changes in a real world is our body temperature. When we have some infections or viral infections, our cells reacts to the foreign substance and fighting it in order to maintain the homeostasis. As a result, the immune system will signal the brain to increase the body temperature thus causing us to be warmer.
Antipyretics on the other hand are medicine used to lower down the temperature of the body. Antipyretics will signal the hypothalamus to control the increased in temperature thus making the fever goes down.