Dean is telling Sam about two "freaky" deaths that occurred in Prosperity, Indiana over the last two weeks. The online article about the first victim, Carl Dunlap, describes the victim's death as being from "hypothalmia", which is not a real term, perhaps the writers meant "hypothermia". Both the next line, and Dean, elaborates that the victim "boiled to death in a hot tub." The correct term should've been either "hyperthermia", a higher than normal body temperature (100.9 °F or above), or even more accurately "hyperpyrexia", the clinical term for dangerously high body temperature (above 105.8 °F). Hypothermia is the clinical term for abnormally low body temperature (below 95.0 °F).