Days of rain in a temperate climate

Clothing does not keep you warm by itself; it holds still air between its fibres. This air insulates. When the fabric gets wet, water pushes out the air pockets, and because water conducts heat much better than air, body heat flows away quickly. When the water then evaporates in the wind, it cools you even more.

On a single rainy day your supply of dry clothing is enough. Over several days, however, hardly anything dries, and every layer you put on eventually gets damp too. That is why, in long wet spells, what decides things is whether you can protect one dry system for the night: sleeping bag, night clothes, socks.

At the same time the landscape changes. The ground soaks up water until it cannot take any more. Then the rain runs off over the surface, streams rise quickly and saturated slopes lose their grip. Trees stand less firmly in softened soil.

No rucksack is waterproof by itself. So pack your sleeping bag, night clothes and electronics in separate waterproof bags. The dry set is only for camp and sleep: in the evening you change, in the morning you climb back into the previous day's wet things. It feels unpleasant, but it is the only way to keep the night clothing dry.

While walking, dress slightly on the cool side. If you sweat heavily inside your rain jacket, you get wet from the inside – even the best jacket cannot let out unlimited moisture. At breaks, on the other hand, put a warm layer under the rain jacket straight away, before you cool down.

Food and warm drinks are not a side issue in prolonged rain. The body needs energy to produce heat. Cooking in the rain is a hassle, but regular warm meals make a big difference. A tarp over the cooking area helps a lot.

In wet-cold weather, hypothermia often creeps in unnoticed. The first signs are shivering, cold and clumsy fingers and a bad mood. Later come stumbling, slurred speech and confusion. Take these signs seriously: get out of wind and rain, change into dry clothing, insulate, eat and drink something warm. If it gets worse, call the local emergency number (112 in the EU).

After days of rain, streams can rise quickly and strongly. You do not cross a stream in flood – you wait or turn back. The US weather service sums this up as „Turn Around Don't Drown“. Check stream crossings and slope sections when planning, and think about alternative routes.

Feet that stay wet and cold for days can be damaged. Dry them in the evening, change your socks and give them time in the air. If they go numb, very pale or painful, seek help. Do not camp below steep slopes or old trees, because in softened ground rocks, soil or trees can give way.

Choose a slightly raised spot, not in a hollow and not right by the stream. Water seeks the lowest path, and a tent in a dip can turn into a puddle at night. Also watch out for deadwood above you.

Put up the tarp first. Underneath it you can set up the tent or sleeping area dry, sort your gear and cook. Wet things do not go into the inner tent but stay in the porch or under the tarp. In long wet spells it pays to plan stages so that huts or fixed accommodation can be reached for drying out.

Many people underestimate wet-cold weather because it is „only“ a few degrees above freezing. But the Wilderness Medical Society explicitly describes that hypothermia occurs without frost when wet and wind combine. Military survival manuals even treat wet-cold conditions as a distinct and particularly treacherous form of cold.

Prolonged rain does have one advantage: water is plentiful. Even rain or stream water should be treated before you drink it, though. And with a good routine – pack dry, change, eat, have an alternative route – even a wet week can be weathered well.