Many Australians associate hypothermia with snow and extreme cold. It is a reasonable association, but it is incomplete. Hypothermia is the result of core body temperature dropping below the range where normal physiological function is maintained. That can happen at an air temperature of 10 degrees Celsius if the person is wet, exhausted, and not generating enough heat to compensate for what they are losing. In Australian conditions, hypothermia risk is highest in wet, windy weather in the ranges, in canyoning where prolonged immersion in cold water is normal, and in high country settings where temperature drops rapidly as weather deteriorates.
How Hypothermia Develops
Core temperature drops when heat loss exceeds heat production. The body loses heat through four mechanisms: radiation (heat radiating from exposed skin), convection (wind stripping warm air from the body surface), conduction (direct contact with cold surfaces, most significantly water), and evaporation (sweating and wet clothing). Wind and wet are the most significant factors in Australian outdoor hypothermia. A combination of rain, wind, exhaustion, and inadequate clothing creates the classic hypothermia scenario in Australian mountains and canyons.
Recognising Hypothermia
Mild hypothermia (core temperature 32-35C) presents as shivering, impaired coordination, slurred speech, confusion, and poor decision-making. The person may deny feeling cold even when clearly affected. Shivering is a sign the body is still generating heat to fight the temperature drop -- it is a good sign in the sense that the thermoregulatory system is active, but it is a warning that the situation needs to be addressed immediately. Moderate hypothermia (28-32C) involves reduced or absent shivering, increasing confusion, muscle stiffness, and potential cardiac arrhythmias. Severe hypothermia below 28C is a life-threatening emergency that requires hospital management.
Treatment in a Field Setting
The field treatment priority is to stop further heat loss and allow the body to rewarm. Remove the person from the source of cooling: get them out of the wind, remove wet clothing if dry replacement is available, insulate them from the ground and around the body. A hypothermic person should not be left alone. If they are shivering and conscious, warm sweet drinks (not alcohol) help energy availability. Insulate with sleeping bags, space blankets, or whatever is available, ensuring insulation from the ground as well as from above and sides.
Handle a moderately or severely hypothermic person gently. Cold myocardium (heart muscle) is susceptible to fibrillation from physical jarring. Do not rub limbs vigorously. Do not encourage the person to exercise. Do not apply heat directly to extremities. The goal is to prevent further cooling and allow controlled rewarming. For moderate to severe hypothermia, activate emergency response and prioritise evacuation to hospital.
Canyoning-Specific Hypothermia Risk
Canyoning combines prolonged immersion in cold water with wet environments, limited ability to self-rescue, and often significant distance from road access. Water conducts heat from the body approximately 25 times faster than air at the same temperature. NSW canyon water temperatures are typically 12-17 degrees Celsius depending on canyon depth, time of year, and recent rainfall. Wetsuits are appropriate for most NSW canyoning. For longer swims and colder canyons, 3mm to 5mm full wetsuits are appropriate. Monitor group members for cold symptoms throughout a canyon, not just at the end.
Prevention: The Practical Approach
- Check the forecast before the trip and specifically check for rain and wind, not just temperature. A 10-degree day with rain and 30km/h wind is a hypothermia risk for an underprepared group.
- Carry a rain jacket and insulating layer that are accessible, not at the bottom of the pack.
- Keep group members eating and drinking. Dehydration and calorie deficit both reduce the body's ability to generate heat.
- Watch your group actively, particularly in deteriorating conditions. Hypothermia impairs judgment, so the affected person may not report feeling cold.
- Know your turnaround criteria and use them. A group that is wet, cold, and two hours from the trailhead needs to turn around before someone becomes a casualty, not after.
- In a canyon, count heads and check condition at every rest point.
Recording Cold Incidents
Any incident where a person showed signs of hypothermia, even mild, should be recorded in LogsKeptSimple with the conditions, the symptoms observed, and what was done. Over time, this data tells you which activities, conditions, and group compositions create vulnerability. A leader who has recorded three incidents where cold became an issue in similar conditions has information that informs future preparation. A leader with no records has to learn the same lessons repeatedly.
