Sleeping outside without a tent

These are listed in the order worth acting on, which with bivvy camping is not the order they are usually presented in.

What it is and is not

A bivvy bag is a waterproof shell over a sleeping bag, providing weather protection and some wind resistance. It adds a little warmth by blocking wind and adds no insulation of its own.

It is not a tent, and in sustained rain it is a considerably less pleasant experience. The material decides most of the experience, because a cheap non-breathable bag traps everything you exhale and leaves the sleeping bag wet by morning, while a breathable membrane costs several times as much and reduces the problem rather than removing it.

Condensation is the trade

Moisture from the sleeper condenses on the inside of the bag, and a fully closed bivvy will leave the sleeping bag damp by morning. Keeping the opening as clear as conditions allow, and using a synthetic or treated-down bag, both reduce the problem.

Over a season, a tarp over the bivvy solves it almost entirely and adds very little weight. Over consecutive nights the effect compounds, since a bag that begins each evening slightly damper than the last loses loft steadily, which is why multi-night bivvying works best where there is enough sun in the middle of the day to dry things out.

Site choice does more work

Without walls, the site provides the shelter, so a wall, a dip, a boulder or a hollow becomes the tent. Cold air pools in hollows overnight, so the lowest point is usually the coldest. Avoiding anything that drips, funnels wind or collects water matters more than it does inside a tent.

In practice, the ground is also somebody's, so lying out of sight of houses and paths, arriving late and leaving at first light is both the courtesy and, in the countries where the legal position is unclear, the practical reason nobody objects.

The advantages are real

Weight and bulk drop substantially, pitching takes seconds, and you can sleep almost anywhere including on ledges and in tight spaces. The experience of sleeping in the open is genuinely different, and most people who do it regularly cite that rather than the weight. It also leaves no trace at all, which suits places where a tent would be conspicuous.

It changes how you use weather as well, because a bivvy can be packed in two minutes and moved, so a forecast that would rule out committing to a pitch becomes a night you can simply relocate if it turns out badly.

When not to

Sustained rain, midge or mosquito season, and very cold conditions all favour a tent by a wide margin. A tarp plus bivvy is the usual compromise and covers most of those except insects. Committing to a bivvy in poor forecast conditions is how people end up walking out at three in the morning.

Insects are the one condition experience does not improve, since a head net keeps them off your face and does nothing for the rest of a night in midge season, which is why committed bivvyers in the wetter west tend to be a spring-and-autumn proposition.

The exception is usually weather, which overrides most planning.

The overnight routine is the part nobody describes

There is no porch, so everything you own is either inside the bag with you or getting wet, and boots, electronics and the next morning's dry layer end up in the sleeping bag or in a dry bag under your knees. Boots left out in a frost freeze solid and take an hour of walking to become properly wearable, which is why experienced bivvyers stuff them into a bag and sleep with them at their feet. Dew forms on anything exposed even on a clear night, so a cloudless forecast is not the same as a dry morning and the outside of the bag is usually soaked by first light.

You wake with the light rather than with an alarm, which in a northern summer means being fully conscious around three, and that is either the best part of the practice or the reason to carry a tent.

Everything above, in order of what to do first

1. What it is and is not. A bivvy bag is a waterproof shell over a sleeping bag, providing weather protection and some wind resistance.
2. Condensation is the trade. Moisture from the sleeper condenses on the inside of the bag, and a fully closed bivvy will leave the sleeping bag damp by morning.
3. Site choice does more work. Without walls, the site provides the shelter, so a wall, a dip, a boulder or a hollow becomes the tent.
4. The advantages are real. Weight and bulk drop substantially, pitching takes seconds, and you can sleep almost anywhere including on ledges and in tight spaces.
5. When not to. Sustained rain, midge or mosquito season, and very cold conditions all favour a tent by a wide margin.
6. The overnight routine is the part nobody describes. There is no porch, so everything you own is either inside the bag with you or getting wet, and boots, electronics and the next morning's dry layer end up in the sleeping bag or in a dry bag under your knees.

The takeaway

Take a tarp as well. It solves the condensation and costs almost nothing.

Go slowly enough to notice, and most of this stops being advice and starts being obvious.