Our body temperature is generally maintained at around 37oC. A build-up of excessive body heat can lead to serious consequences. Overheating the body can cause serious impact to the brain - generally known as "heat stroke". Heat stroke victims must be treated without delay. The most basic rule is to help the victim dissipate body heat. Heat stroke can cause death within a very short time, so treatment must be speedy.

Overheating results from extreme or prolonged exposure to heat. As the body tries to rapidly dissipate the excessive heat, the blood vessels near the skin surface expand. This results in the blood supply to the brain and other vital organs running low, and so the victim looses consciousness. Early signs of overheat are dizziness and palpitations, followed by nausea, vomiting, headache, restlessness and finally unconsciousness. The obvious symptoms are cold sweaty skin and abnormally low body temperature.

Heat stroke is caused by poor sweating and heat dissipation. When we work in extreme heat for an extended period, the function of our sweat glands will slow down or even stop. This prevents proper heat dissipation. At the onset of heat stroke, the victim feels very hot. This uneasiness is quickly followed by an unclear mind, disorientation and finally unconsciousness. Obvious signs are a high body temperature exceeding 105oF and very warm skin with no sweat.

It is a common belief that periodic intake of salt can make up the loss caused by exercising in hot weather. The truth is, our normal diet contains sufficient salt to restore a healthy level. Unless you are in high temperature continuously for three or more days, there is no need to take any salt supplement. As pure salt absorbs water, it is not advisable to take salt tablets. To avoid stomachache, drink warm water with salt instead.

We lose a considerable amount of moisture when we engage in outdoor activities in hot weather. It is crucial to replenish water and salt. There is a common misconception that drinking too much water will reduce the level of salt and minerals. The truth is quite the contrary. Drinking water is a good way to replenish body moisture and minerals.

Cold distress or "hypothermia" often occurs when the hiker is not adequately protected by thermal clothing. It can also be a combined effect of hunger and cold. The victim will feel chilly, reflexes become slow, and other symptoms like haziness, grumpiness, abnormal behaviour, wobbliness, convulsion and shivers soon set in. To prevent cold distress, wear good thermal clothing and protect yourself with extra clothes when you stop to rest. Eat nutritious food along the way to ward off hunger.

In spring, thick mists are common in Hong Kong's countryside. On a bad day, visibility can be down to a few feet. Hiking in this kind of weather calls for extra care. Before entering an area with thick mist, make sure you know your exact position, and note the local environment and scenic features to help identify your present location. If the area you are in suddenly becomes misty, stay calm. Try to find a return path. If your fellow hikers are tired or you are uncertain about the return path, the safest thing is to stay put in a nearby sheltered place and wait for help.

Lightning usually strikes the land at abrupt high peaks or exposed ridges. The great electric current does not stop at the contact point, but is conducted to the ground for a further distance before finally dying out. Hikers are more likely to be hit by the ground current than struck by the actual lightning.

Hong Kong has almost no rivers, but there are many streams and watercourses in our countryside. Heavy rain can turn trickling streams into raging torrents. Never underestimate the force of these fast and devastating torrents. A rushing waterway the depth of your ankles is powerful enough to throw you off your feet, while knee-deep water can wash away water buffaloes and other large animals. Never hike along a river valley, stream or basin, and don't wade across streams, catchwaters or dams. Following heavy rain, steep or weathered slopes are potentially hazardous. To avoid the danger of landslides, finds a safer route. If there is a landslide, stay calm. Seek shelter in a safe place high up, and hold on to a tree or large boulder. Never run in panic or act alone.