Winter daylight is the planning constraint people forget

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

The arithmetic is unforgiving

At temperate latitudes midwinter gives a fraction of the usable daylight of midsummer, and less in poor weather. A route that takes seven hours in summer takes longer in winter conditions, on the shorter day.

Those two effects compound rather than add, which is what catches people out. The arithmetic also scales sharply with latitude, so the same date gives a very different working day in the Alps and in northern Scotland or Scandinavia, and a plan carried from one to the other without recalculating is built on somebody else's daylight.

Start earlier than feels reasonable

Starting at first light is the single most effective winter planning decision. It requires driving or travelling in the dark, which is why it is resisted and why it works.

On the ground, finishing with daylight in hand is the objective rather than starting comfortably. It works because the darkness gets spent on the easy part, since walking an approach track by torchlight is straightforward while descending broken ground in the dark is not, so an early start simply moves the dark hours to where they cost least.

Conditions slow everything

Snow, ice, mud, wind and short visibility all reduce pace, sometimes substantially. Navigation takes longer in poor visibility, and stops for layers and food take longer in cold.

Applying a summer timing to a winter route is the underlying error. The specific time sinks are small and endlessly repeated: stopping to fit and remove crampons, taking gloves off to deal with a strap or a map, and eating food that has frozen solid, none of which appears in any timing formula.

Turnaround times, not turnaround points

Setting a time at which you will turn back regardless of where you are removes the negotiation on the hill. Distance-based objectives encourage pressing on because the summit is close. Time-based ones are the mechanism experienced parties use.

Worth knowing before you go — the time itself should be worked backwards from how long the descent takes rather than set at the halfway point, because it is the way down that has to fit inside the remaining light and it is rarely half the day.

Carry the torch you hope not to use

A head torch with charged batteries converts an unplanned dark descent from an emergency into an inconvenience. Spare batteries matter more in cold, which reduces capacity. One per person, not one per party, because groups separate.

In practice, the spare cell belongs in an inside pocket rather than in the pack, both because it holds its capacity there and because changing a battery on a dark hillside with cold hands is a job worth having practised once at home.

That varies by region, and it is worth checking locally.

Twilight is real daylight, and its length depends on latitude

Usable light starts before sunrise and lasts after sunset, so the workable day is longer than the printed sunrise and sunset times imply, and under clear skies it is longer by a useful margin. How much longer depends on latitude: twilight is drawn out at high latitudes and adds a genuine buffer at each end, while close to the equator the light goes from usable to gone in well under half an hour. That catches travellers out in both directions — someone used to lingering northern evenings gets caught by a tropical sunset, and someone used to abrupt darkness wastes light that was available further north.

Cloud, tree cover and a deep valley all cut twilight short, so those times are an upper bound rather than something to plan the last leg around.

Everything above, in order of what to do first

1. The arithmetic is unforgiving. At temperate latitudes midwinter gives a fraction of the usable daylight of midsummer, and less in poor weather.
2. Start earlier than feels reasonable. Starting at first light is the single most effective winter planning decision.
3. Conditions slow everything. Snow, ice, mud, wind and short visibility all reduce pace, sometimes substantially.
4. Turnaround times, not turnaround points. Setting a time at which you will turn back regardless of where you are removes the negotiation on the hill.
5. Carry the torch you hope not to use. A head torch with charged batteries converts an unplanned dark descent from an emergency into an inconvenience.
6. Twilight is real daylight, and its length depends on latitude. Usable light starts before sunrise and lasts after sunset, so the workable day is longer than the printed sunrise and sunset times imply, and under clear skies it is longer by a useful margin.

The takeaway

Start at first light and set a turnaround time. The daylight is the budget.

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