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Snowshoeing: What Size Dry Bag Do You Need?

Why snowshoeing is a sweat problem, not a rain problem

Snowshoeing is the most consistently damp winter activity there is, because the water comes from inside the system rather than from the sky. A 70 kg adult moving at 3 km/h through 30 cm of fresh snow burns roughly 400 to 550 kcal an hour and produces 300 to 500 ml of sweat in the same period. Almost none of that evaporates through a hard shell, so it sits in the base layer until you stop moving.

The moment you stop, that moisture starts to migrate. Take the shell off at a viewpoint and the damp base layer begins to cool; put the shell back on for the descent and the moisture is now between you and your insulation. A dry bag does not stop you sweating, but it does guarantee that the spare hat, mittens and mid-layer you reach for at that viewpoint have never touched anything damp.

External water is comparatively minor. Snow falls off a shell, spindrift only matters above the treeline, and there is no immersion event unless you punch through a bridge on a hidden creek. That is why the sizing logic here is different from paddling: you are buying volume for a wet layer and a dry layer, not protection against a dunking.

Sizing by outing length: from a two-hour loop to a full day

Pick a size from the clock rather than from the gear list. The single biggest variable on a snowshoe outing is how long you are out, because insulation requirements climb steeply once you pass four hours and the light starts to go. A two-hour loop at midday in full sun needs almost nothing; the same loop starting at 15:00 in January needs a full insulation set.

Notice that the 5L bag appears in every row. That is not an accident: a 5L roll-top is the right home for the one wet layer you peel off mid-morning, and it stays useful on the longest trips. If you own one winter dry bag, make it a 5L; if you own two, add a 10L for the insulation set.

The wet layer and the dry layer never share a bag

The discipline that makes winter snowshoeing comfortable is a strict two-volume split. The dry volume holds the insulated jacket, spare mittens, a hat, a neck gaiter, the first-aid pouch and any electronics. The wet volume holds what you took off: a damp base layer, wet socks, a soaked neck gaiter, and later in the day the mittens that got snowpacked at a stream crossing.

On a half-day outing the dry volume is about 6 litres and the wet volume about 3 litres, which is why a 10L and a 5L pair so well. Putting both in one 15L bag is technically possible and practically wrong, because opening that bag at a windy viewpoint to throw in a wet base layer exposes the insulation to falling snow and costs you heat every time.

Where the bag sits: daypack, sled or shoulder carry

Most snowshoers carry a 25 to 35 litre daypack and the dry bags go inside it. Place the dry bag against the back panel where your body heat keeps the closure from freezing, and place the wet bag in the outer pocket or under the lid. This is the opposite of summer practice, where wet gear goes as far from your back as possible, and the reason is simple: a frozen closure is a bigger problem than a damp back panel.

A pulk or a child sled changes the calculus completely. Sleds throw slush continuously along the tow lines and the sides, so anything on a sled needs a welded bag with the closure facing up and away from the spray, and it needs to be lashed at two points to the frame. A 30L or 40L dry bag works well here, and the extra capacity is cheap because the sled is carrying it, not you.

Cold: film, buckles and the temperature you stop folding at

Below freezing the limiting component is not the fabric, it is the fold. A 0.5 mm TPU film on a 420D face stays workable to roughly minus 20 °C and can be rolled with two hands; the same thickness in PVC coated fabric goes board-stiff near minus 10 °C and forcing a fold will crease it permanently. Buy for the coldest morning you actually go out in, not the average.

Hardware fails sooner than film. Side-squeeze buckles made from acetal get brittle near minus 25 °C and the tongue can crack if it is levered rather than squeezed. Grit from trail salt or frozen mud accelerates that. Warm a stubborn buckle inside a jacket for thirty seconds and squeeze with the palm, and carry one spare buckle in the repair pouch if you are out for a full week.

Closing a roll-top with mittens and no feeling in your hands

The technique that works in winter is a palm press rather than a finger pinch. Fold once along the mouth, then run the heel of the hand along the full width of the fold so it seats evenly, fold again, press again, fold a third time and clip. Three folds remain the standard: two will hold falling snow but not the melt water that pools where the fold sits against a warm pack panel.

Clear the mouth first. Tap the bag upside down twice to drop loose snow, then brush the fold line with a gloved hand before the first fold. If snow is already inside the fold, leave it: a bag rolled with a little snow inside stays damp for a day but survives, whereas a frozen fold wiped with a bare wet glove will stiffen and crack. Deal with it properly that evening indoors.

Waterproof ratings for snow, slush and stream crossings

Snow contact is a mild exposure and it is worth being honest about that. A dry bag inside a daypack on a forest trail will never face a water jet or an immersion, so the rating that matters is seam construction and closure cleanliness. Welded seams wick nothing; a stitched seam with a coating will pass a shake test and then wick melt water for as long as damp snow sits against it, which on a four-hour outing is four hours.

There are two exposures that do justify a step up. The first is a sled, which throws slush at speed and is effectively a low-pressure jet event. The second is a spring creek crossing, where a slip puts the bag under for a few seconds. Both are covered by an IPX6 or IPX7 welded bag, and the test language behind those grades is defined by the IEC rather than invented by whoever writes the hang tag.

The last row catches people out. A bag that spends the night in a porch goes through a freeze-thaw cycle that no ingress test replicates, and the strain lands on the fold. Roll it loosely and keep it off the ground if you know it will be out overnight; a tightly rolled, frozen bag is how a crease becomes a split.

What fits in 5L, 10L and 20L on a winter trail

Winter gear is bulkier per gram than summer gear, so summer volume intuition misleads. A 640 g insulated jacket occupies about 5 litres loosely packed and 3 litres compressed, and a pair of winter mittens plus a hat plus a gaiter fills most of a 5L bag on its own. The table lists items packed as they would be on a trail, not vacuum-compressed.

Read the bottom row carefully. A full winter day with a stove and a camera does not fit in a 10L bag, and trying to make it fit is how closures get over-filled and leak. If you regularly carry a stove and optics, the 20L plus 5L pairing in the sizing table is the honest answer, and the 10L is the right size only for the half-day forest loop.

Weight, and the 10% rule for a winter day

Snowshoeing is low-impact and slow, which means it tolerates more weight than running or skiing but punishes badly distributed weight. The practical rule is to keep the total carried load under 10% of body weight, so a 70 kg snowshoer should be at 7 kg or below including water, food and the bags themselves. Two dry bags add 250 to 400 g to that budget.

Where you cannot stay under 10%, put the heavy items close to the shoulder blades. A 3 kg bag slung low and away from the back panel levers on the lumbar spine with every step through deep snow, and after five hours that is the difference between a good day and a sore week. This is the same reasoning that applies on the water, and it is covered for paddlers in our carry comfort guide.

Water, snacks and the frozen bottle problem

A standard 750 ml bottle of water at minus 10 °C starts to form ice within ninety minutes and is largely solid by three hours, which is why so many winter snowshoers arrive at a viewpoint with no drinkable water. Insulate the bottle inside the dry bag rather than outside it: wrap it in the spare jacket or a hat and it will stay liquid for four to five hours.

Alternatively carry the bottle inverted, because water freezes from the top down and the cap is the first thing to lock. Either way, do not put a wet bottle straight into the dry bag with electronics; wipe it, cap it, and give it its own corner. Snacks belong in a lid pocket rather than in a dry bag, because a bag opened six times for a snack is a bag that is never properly closed.

Electronics: the warm-body rule still wins

A phone at minus 10 °C loses around 40% of its runtime and many models shut down entirely below minus 20 °C regardless of charge. The countermeasure is body heat, not a better bag. Carry the phone in an inside jacket pocket, and use the dry bag for the spare power bank wrapped in insulation, where it will hold roughly 70% of its rated capacity at minus 5 °C.

Condensation is the other electronics risk, and it happens at the end of the day rather than in the middle. A cold phone taken into a warm hut, or sealed inside a cold bag that then warms up, collects moisture on and inside the device. Let the bag reach room temperature before you unseal it, and leave the phone in its pocket until you are indoors and dry.

After the outing: thawing, drying and off-season storage

1. Bring every bag indoors and let it reach room temperature before opening; thirty minutes is typical for a 10L.
2. Open, turn inside out and wipe the interior; expect 20 to 40 ml of condensation in a 10L bag.
3. Rinse the fold line with fresh water if the bag has seen trail salt or muddy slush.
4. Dry in a ventilated room with the mouth open, away from a direct radiator or a wood stove.
5. Work each buckle through its full travel while it is still damp, then dry the hardware.
6. Store loosely rolled with the buckle unclipped, in a dark cupboard, for the off-season.

Wood stoves and radiators are the two things that kill winter bags faster than the trail does. Direct heat dries the film unevenly, stiffens the fold and can soften a weld line; a hut stove can reach 200 °C on its top plate, which is far past what any laminated fabric tolerates. Air drying at room temperature overnight is enough, and detailed steps for the closure itself are in our roll-top cleaning guide.

Off-season storage deserves one line of its own. Seven months in a hot garage does more damage than three months on the trail, so store dry bags rolled loosely, dark, and off a concrete floor where they will not pick up moisture. Our off-season storage notes cover the temperature and humidity targets, and the same advice applies to any waterproof bag in the range.

Choosing between two sizes: the decision rule

• Buy for the longest outing you do regularly, not the one epic day you plan each winter.
• If you own one bag, make it a 5L; if you own two, add a 10L.
• Pick 0.5 mm TPU over PVC whenever the bag will fold below minus 10 °C.
• Confirm the buckle releases with a mitten on before you leave the shop.
• Choose welded D-rings if the bag will ever be lashed to a sled or a pack frame.
• Keep snacks and water out of the dry bag so the closure is opened less often.
• Check the cold-flex figure on the spec sheet, not just the waterproof adjective.

If you are still between two sizes after that list, choose the larger one. An underfilled dry bag rolls more times and seals better; an overfilled one cannot seal at all, and the failure is silent until you open it at the car. Compare the candidate sizes side by side in the roll-top dry bag range, where 5L through 90L share one fold geometry.

For clubs, guiding operations and rental fleets the same seven lines become a procurement brief: volume, film thickness, seam type, hardware grade, colourway and the cold-flex data behind the waterproof claim. Waterproof bag production has run at our SGS-verified 4,950 m2 facility since 2014, with a 500-piece minimum, sampling in 6 to 10 working days and bulk in 35 to 50 days.

Cold exposure is the risk no bag manages for you. Wet insulation, wind and a long walk back to the car is the classic hypothermia sequence, and the CDC publishes the early signs and the response every winter walker should recognise. Check the wind chill and the freezing level through NOAA before you set out, and see the backcountry skiing guide if your winter also includes days on skins.