“Is a heat stroke an emergency?”

Yes

Depends on your symptoms. If you are confused, disoriented, if you actually passed out then yes....go immediately to the ER. If you felt better after you took a break out of the heat and hydrated yourself, then learn from your experience and in the future, take more frequent breaks and be sure you are well hydrated at all times.

Heat stroke is a lethal medical emergency if not aggressively cooled. The term, however is frequently overused--as likely your case--and should more properly be termed heat exhaustion.Anyone who overdoes it in the heat, particularly with direct sun and/or inadequate hydration, will tend to feel "wiped out," very fatigued, and listless. That is exhaustion. Heat stroke generally is accompanied by a markedly elevated body temperature, due to the failure of autoregulation, sometimes reaching 106-109F. In part as a consequence of this high temperature, the patient is usually delerious, and some sources require altered mental status with temperature elevation given a history of heat exposure to confirm heat stroke. This condition must be rapidly cooled, and the subject often has some associated muscle tissue breakdown, so is generally hospitalized for further care.