Heat and cold at the destination: take the first days carefully

The body keeps its core temperature within a narrow range. In heat it releases warmth mainly by evaporating sweat. With repeated, moderate activity in the warmth it adapts: it starts sweating earlier, cools more effectively and copes better with the strain. This adaptation, acclimatisation, develops over days to about two weeks.

Until then the body is more vulnerable. A programme that would be easy at home can be too much in the first week in the heat. High humidity adds another factor: sweat evaporates less well, cooling works less well, and the strain feels considerably higher than in dry heat at the same temperature.

There is hardly any physical adaptation to cold that is really sufficient. Here protection from outside is what counts: several layers of clothing, hat and gloves, staying dry and protecting yourself from wind and wet. Wet clothing, especially cotton, loses much of its warming effect.

Plan the first days gently. Do not schedule strenuous tours on the day of arrival and increase exertion slowly over several days. In heat, use the cooler morning and evening hours and rest in the shade at midday.

Drink throughout the day and do not wait until you are thirsty. The colour of your urine is a simple guide: very dark urine suggests you should drink more. With heavy sweating you also lose salt; normal meals help replace it. Mind the local water quality and only drink water that is safe. Alcohol is not refreshment in the heat but an extra strain.

Dress appropriately. In heat, light-coloured, loose clothing, a hat and sun protection help. In cold, layers you can put on and take off depending on exertion, a hat, gloves, wind and rain protection and dry spare clothing help.

In heat, headache, dizziness, nausea and severe exhaustion are signals to stop: get into the shade, rest, drink. Confusion, altered consciousness or collapse may indicate heat stroke. Then call the local emergency number (112 in the EU) immediately, move the person into the shade and cool them.

In cold, strong shivering, numbness, clumsiness, confusion or striking apathy are warning signs of hypothermia. Protect the person from further heat loss – out of wind and wet, dry clothing, insulation – and call for help. Treating heat stroke and hypothermia belongs in the hands of the emergency services.

Look out not only for yourself but also for fellow travellers. Young children, older people, pregnant women and people with cardiovascular disease or certain medications are especially at risk in heat. Anyone with pre-existing conditions should get medical advice before the trip. And: never leave children waiting in the car – a parked car heats up very quickly in the sun.

The classic: arriving in a warm holiday country, with a long sightseeing tour in the midday sun or a hike planned for the very first day. Better is a quiet first day with short distances, with the big programme coming later. That does not make the holiday shorter, just more pleasant.

Conversely, many people underestimate how cold it can get on desert nights, in the mountains or in wind and rain by the sea. Anyone travelling from summer into winter should bring clothing for real cold, not just a thin jacket. Altitude is a separate topic with its own rules and is not covered here.