Consciousness begins to be affected — judgment is impaired, coordination is compromised, and the person may become confused or irrational.

The heart rate slows.

The breathing rate slows.

In severe hypothermia (core temperature below 82.4 degrees Fahrenheit, or below 28 degrees Celsius), the situation becomes critical.

Cardiac arrhythmias become more likely — the cold disrupts the electrical signaling system of the heart in ways that can produce dangerous or fatal rhythm disturbances.

Consciousness is profoundly impaired or absent.

The heart rate is very slow.

Breathing is very slow or absent.