Accidental hypothermia is potentially fatal. It can happen as simply as falling off a log. Falling into icy water, or exposure to cold weather without appropriate protective clothing, can quickly result in death. Hypothermia is classified into four states. In mild cases 95–89.6°F (35–32°C), symptoms include feeling cold, shivering (which helps raise body temperature), increased heart rate and desire to urinate, and some loss of coordination. Moderate 87.8–78.8°F (31–26°C) hypothermia causes a decrease in, or cessation of, shivering; weakness; sleepiness; confusion; slurred speech; and lack of coordination. Deep hypothermia 77–68°F (25–20°C) is extremely dangerous as the body can no longer produce heat. Sufferers may behave irrationally, become comatose, lose the ability to see, and often cannot follow commands. In profound cases 66–57°F (19–14°C), the sufferer will become rigid and may even appear dead, with dilated pupils, extremely low blood pressure, and barely perceptible heartbeat and breathing. This state usually requires complete, professional cardiopulmonary resuscitation for survival.