Your warm layer has to do three things: keep you warm at rest stops and in cold weather, keep insulating even when it’s damp, and pack down small enough to fit in a day rucksack.

For active use, start with the Rab Xenair Alpine Light, a synthetic jacket in a men’s or women’s listing.

Its insulation is light, so it is not a complete answer for a long stop in winter.

Choose synthetic where damp is likely and down for dry stops.

A jacket alone does not make winter summit walking safe.

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Four jackets, five listings, by filling, fit and use:

Your day out What to carry
You want synthetic filling you can wear while climbing and at stops Rab Men's Xenair Alpine Light Jacket
You want the same design in a women's listing Rab Women's Xenair Alpine Light Jacket
You want a hooded synthetic jacket that packs small Berghaus Men's Vaskye Jacket
You want an insulated hood and stretch fleece side panels Montane Women's Icarus Lite Hooded Jacket
Your stops are dry and you want down that packs small Rab Women's Microlight Alpine Down Jacket

The jackets

Rab Men's Xenair Alpine Light Jacket

You want a synthetic jacket to wear on the climb and put on at every stop

Rab Men's Xenair Alpine Light Jacket PrimaLoft Gold Active+ synthetic fillingClose-fitting hood, centre-front zip Read the full specification on Amazon

Rab lists PrimaLoft Gold Active+ (PrimaLoft is a maker of synthetic filling) in two weights, lighter in the areas that run hot.

It is made for use while moving.

The zip runs down the centre of the front, and the hood is close-fitting.

This light active jacket is not a complete answer for a long winter stop. It suits cool climbs and brief halts.

Rab Women's Xenair Alpine Light Jacket

You want the same design in a women's listing

Rab Women's Xenair Alpine Light Jacket PrimaLoft Gold Active+ synthetic fillingClose-fitting hood, centre-front zip Read the full specification on Amazon

The maker’s page gives the women’s jacket the same PrimaLoft Gold Active+ filling, centre-front zip and close-fitting hood.

Synthetic filling suits damp days.

Use it for moving and brief stops; do not rely on it alone for a long winter stop. Choose a size from the women’s size chart.

Berghaus Men's Vaskye Jacket

You want a hooded synthetic jacket that packs small

Berghaus Men's Vaskye Jacket Synthetic Hydroloft Polyball fillingAdjustable insulated hood, front zip Read the full specification on Amazon

Berghaus lists its own synthetic filling, Hydroloft Polyball (fine polyester fibres), held in small stitched sections called micro baffles.

It calls the insulation water resistant and the jacket very compressible.

The hood is insulated and adjustable, and a soft chin guard stops the zip rubbing.

It is not listed as waterproof, so in rain wear a waterproof over it.

Montane Women's Icarus Lite Hooded Jacket

You want an insulated hood and stretch fleece side panels

Montane Women's Icarus Lite Hooded Jacket PrimaLoft ThermoPlume and Silver synthetic fillingInsulated hood, stretch fleece side panels Read the full specification on Amazon

Montane says ThermoPlume, a loose synthetic fill, mimics down but keeps its warmth when wet.

A sheet of PrimaLoft Silver helps prevent the fill shifting.

The hood is insulated, and the front zip runs full length with an internal storm flap (a fabric strip behind the zip).

The side panels are stretch fleece, a soft knitted polyester. The outer fabric is water repellent, which is not the same as waterproof.

Rab Women's Microlight Alpine Down Jacket

Your stops are dry and you want warmth that packs small

Rab Women's Microlight Alpine Down Jacket 700 fill-power recycled downWomen's fit for dry-weather stops Read the full specification on Amazon

Rab lists 700 fill-power recycled down.

Fill power describes how much space down takes up for its weight.

Rab says down gives the most warmth for its weight and compresses easily.

Keep this one dry. Rab recommends synthetic filling for damp conditions.

Synthetic or down, by the kind of day

Synthetic filling is man-made fibre. Down is the soft under-feather of ducks or geese.

Rab recommends synthetic for damp conditions and down for warmth for its weight and how small it packs.

  • Drizzle, mist or a rucksack that may get wet: synthetic.
  • Cold, dry stops and a small pack: down, kept dry.
  • One jacket for climbing and stops: synthetic, such as the Xenair.
  • A setback that keeps you still: keep every spare layer dry, and choose synthetic when damp is likely.

Wearing it over or under the waterproof

None of these jackets is waterproof. In rain, wear the waterproof outside so the filling stays dry.

Which one fits over the other depends on the size of both garments, so try them together.

A padded jacket being placed inside a dry bag beside an open rucksack.

A dry bag (a waterproof sack) keeps a spare jacket dry in the rucksack.

That matters most for down.

Do you need one at all?

A warm fleece and a waterproof may be enough, provided they keep you warm enough for the forecast and the length of your stops.

A padded jacket adds filling and a wind-resisting outer fabric, which suits longer or colder stops.

A jacket alone does not make winter summit walking safe. Conditions, skills and the rest of your kit matter as much.

We compile and explain public route and safety information. We guide nobody and sell nothing on the hill.

Which jacket for a damp day, which for a dry stop

Pack the jacket with the rest of what to pack for a walk in Snowdonia, and add a merino base layer beneath it.

Winter conditions need more than a jacket, as anyone planning Snowdon in winter will find.

If you plan to be on the summit for Snowdon sunrise, pack the jacket for the wait.

Choose synthetic where damp is likely, such as the Xenair, Vaskye or Icarus Lite, and choose the Rab Microlight Alpine Down only for dry stops, kept in a dry bag until you stop.