Heat risks are wide ranging and guidance needs to cover many circumstances.
This section of the site does not claim to give all the information you need, but it does illustrate some of the key issues.


When physically working or exercising in very hot conditions, both dry and humid, heat stroke is the most damaging and potentially lethal cause of illness.
Heat stroke takes hold very quickly, and unless treated immediately and effectively it will kill. Heat stroke's fatal effects can happen in a very few hours and must be treated in situ. Even tropical diseases take a few days to become life threatening and unlike heat stroke give time for evacuation to hospital.
When going on holiday, expedition, or work party to a hot climate, and especially one with high humidity, an acclimatisation period of 14 days is required. Initially during acclimatisation the work load or exercise pattern must be low, and carried out in the cool of the day. Gradually exercise should be built up to full work load in hotter conditions. During this 14 day period the body adapts its cooling system [ extra blood produced, greater sweating, less salt loss ].
After acclimatisation it is still possible for an acclimatised person to produce, due to exercise, more heat than the body can dissipate and heat illness will occur.
Exercise during sudden hot spells in temperate climates and during events like raves in hot recreational environments will be dangerous if the participants have not had time to acclimatise and the environmental temperature is high.

"Must Reads" are the main symptoms and treatments as outlined in those sections of the web site


1. The hotter it is, the more the body relies on sweating to dissipate heat
2. The more humid it is, the less effective sweating becomes.
3. Uneven work i.e pulling, digging, chopping etc generates twice as much body
heat as the equivalent walking and running.
4. In a hot shaded environment loose light clothing with arms and legs exposed
will aid cooling, better bitten than suffer heat stroke.
5. Hats when worn [ preferably under direct sun ] should be light and porous as
the head is a major source of body cooling.
6. The first week of acclimatisation is especially dangerous.
7. It is essential to keep both water and salt levels up as extra blood and sweat
has to be produced for additional cooling.
8. Vegetarians and those who add no salt to their food should increase their
salt intake before leaving for hot climates, as low salt levels can interfere
with acclimatisation and increase heat illness risks.
9. If the destination involves jet lag extra care should be taken during acclimatisation
10. Sudden very high temperatures in normally temperate countries are as dangerous
as the first week of acclimatisation.
9. Always work or exercise with a buddy so you can keep an eye on each other
for signs of heat stroke - the most dangerous signs are mental confusion & nausea.
Don't treat headaches with pills - immediate cooling should be commenced.
10. Always suspect heat related illness as it is the most likely cause in hot climates
and treat accordingly.
Risk starts at +2 oC above normal body temperature, and +4 oC can cause
permanent damage or even death.
11. For 20 minutes after exercise has stopped the body's chemistry continues
to produce extra heat.


Are there medical and or first aid personel provided by the organisation ?
Are such staff located near the activities ?
Have medical or first aid personel been trained in the specific techniques of recognising and treating heat stroke ?
Have they been trained in the last 12 months ?
What is the acclimatisation period ?
What time of day will exercise occur, especially in the first week ?
Is jet lag allowed for ?
Does the diet have suitable salt content ?
Does the organisation have a way of measuring temperature and humidity ?
Do they adhere to the "exercise in heat" tables issued by the Royal Geographic Society ?
Will they have access at all times to medical thermometers and supplies needed for diagnosis and treatment ?
Do they have evacuation plans for serious medical incidents ?
Do these plans allow for the difficulties of night evacuation ?
For large parties of people [ 15+] do these plans allow for the possibility of 2 serious incidents and evacuations within 24 hours ?


* Those with increased fat under the skin which insulates and reduces heat loss - those overweight for their height and females.
* Small light people as for an equal amount of work or exercise they heat up faster.
* Those who sweat little, suffer from prickly heat, or cannot handle heat at the best of times.


* Females' body temperatures are raised in the early part of their menstrual cycle.
* Anyone who has suffered a cold or fever should avoid exercise in the heat until 5 days after the infection has passed.