Staying dry in prolonged rain: wet and dry zones

Clothing and sleeping bags keep you warm because they hold still air between their fibres. When the material gets wet, water fills these spaces. Water conducts heat much better than air – that is why you cool down so quickly in wet clothing, even when it is above freezing outside. Down fill collapses badly when wet; synthetic fibres keep somewhat more warmth but also get worse.

Moisture reaches your sleep system in three ways: from above as rain and drips, from inside as condensation from your breath, and from wet items you carry in. Something different helps against each of these: a tight roof, good ventilation and a strict separation of wet and dry.

The big advantage of this routine: as long as the sleeping bag is dry, you can warm up again at night even after a completely rained-out day. Your body recovers, and the next morning you start with reserves instead of already chilled.

Packing starts at home. A backpack is almost never truly waterproof, not even with a rain cover. Sleeping bag, sleep clothes and electronics therefore belong in their own dry bags or in a large, strong liner, for example a sturdy bin bag. That way they stay dry even if the backpack is soaked.

When pitching in rain, order matters. If possible, the roof goes up first – tarp or fly – and only underneath it do you unpack. Then decide where the wet zone is: the vestibule or the edge under the tarp. That is where you take off your rain jacket and boots before crawling into the dry interior.

One set of clothing belongs to the night only. Never wear it during the day, even if it is tempting to slip into dry things in the morning. Otherwise you will have nothing dry left the next evening. Wet socks do not dry in the sleeping bag; they make it damp.

Wet is one of the main causes of hypothermia, even at temperatures above freezing. Watch for persistent shivering, clumsiness, confusion or listlessness – in yourself and others. With such signs, dry clothing, protection from wind and wet, food and if necessary help via the local emergency number (112 in the EU) are what help.

In persistent rain, streams and small rivers can rise very quickly, sometimes also because of rain falling further up the valley. Do not camp in gullies, hollows, dry stream beds or right on the bank, and heed flood warnings.

It is very tempting to cook or heat inside a closed tent to dry things. That is dangerous: stoves can produce carbon monoxide, an invisible, odourless gas, and tent fabrics burn quickly. Cooking happens outdoors or under a well-ventilated tarp with plenty of distance from the fabric – and only where it is permitted.

In a tent, a lot of condensation often forms in rain because the air outside is already humid. Keep the vents open anyway and wipe the inside of the fly with a small cloth before the drops fall. Make sure the sleeping bag does not touch the tent wall.

In a hammock camp, rig a line for wet clothing under the tarp – but outside the lying area so nothing drips on you. Small drip lines on the suspension make rainwater drip off the rope instead of running into the hammock.

Every break in the rain is valuable. Hang sleeping bag and clothing up briefly to air, even if the sun is not shining – wind dries things too. Pack everything away again in time before the next shower comes.

The wet-and-dry routine is worth it on every multi-day trip in rainy regions, whether with a tent, tarp or hammock. It costs hardly any extra weight – a few dry bags – but it demands discipline, especially when you are tired and chilled.

It does not replace retreating in floods or severe weather. Anyone who notices that the sleep system can no longer be kept dry should turn back in good time or seek out a hut rather than risk another wet, cold night.