A woman in her 70s experienced severe heat stroke after a 45-minute sauna session, causing her body temperature to dangerously rise to 107.6°F. She was hospitalized with multiple complications including seizures and kidney injury but eventually made a full recovery.

“Once heat stroke has occurred, the key determinate of outcome is how rapidly a patient is cooled, as the time spent with elevated core body temperature is correlated to the degree of cellular damage,” McIver concluded. Harvard Medical School has more on heat strokes.

"Sauna use is a rare but potentially important cause of classical heat stroke," the doctors of a new case report warn.

Heat stroke is defined as a sharp increase in core body temperature above 40C that is associated with acutely impaired brain function.