Quick answer

Buy on Boxing Day only once the bag has passed the label check. Boxing Day 2026 is Saturday 26 December, and the big UK outdoor chains do not publish their sale dates, so the calendar cannot settle it. What can: a tested temperature in degrees Celsius. Aim for a comfort figure a few degrees below the coldest night you expect, budget for an insulating mat under it, and for a winter bag, treat no tested figure at all as no purchase.

Table of contents

Why the timing question has a real answer

Boxing Day 2026 falls on a Saturday, 26 December, so GOV.UK lists the England and Wales bank holiday as Monday 28 December. If your plan involves a drive to a retail park rather than a laptop, the sale day and the bank holiday are not the same day.

What nobody can tell you is when the discounts land. On 9 September 2026 the sale pages of the big UK outdoor chains carried no dates at all: GO Outdoors and Mountain Warehouse both run one with no start or end date, and Blacks has no sale page at that address. Any sale calendar you find online is a guess, not a commitment.

What is fixed is the shape of the season: Black Friday 2026 is Friday 27 November, four weeks and a day earlier. So the useful question about a reduced bag is not whether a better price is coming, but whether it is the right bag.

What comfort, limit and extreme actually mean

A rated bag does not carry one number, it carries a set, and the standard behind them is BS EN ISO 23537-1:2022, current since 31 July 2022. Its predecessor, BS EN 13537, has been withdrawn, though one large UK chain's live buying guide still offers "The EN 1357 comfort rating system" as the reference, a garbled number.

The definitions below are from ISO 23537-1:2016; the 2022 text is paywalled.

  • Comfort: the "lower limit of the comfort range, down to which a sleeping bag user with a relaxed posture ... is globally in thermal equilibrium and just not feeling cold".
  • Limit: the same wording for a user "with a curled up body posture", which Rab describes as someone "fighting against the cold". The band between it and the extreme figure is what the standard marks as the risk range.
  • Extreme: a "very low temperature where the risk of health damage by hypothermia is possible", with the standard's own note adding "This is a point of danger which can lead to death".

None of which is compulsory. Mountain Equipment says the standard is "not legally binding", and no UK law requires a bag to be rated at all.

Rab names its bags after the limit of comfort and Alpkit quotes a limit temperature in its straplines, so on both the headline number is the curled-up one. Rab's Ascent Down Sleeping Bag is named for a 0°C limit; its published ISO figures are comfort 5°C, limit 0°C and extreme -15°C. Down loses insulation when wet; synthetic keeps insulating when damp. Our hot water bottle guide runs the same comparison for a bag you already own.

One line of the standard's scope decides a lot of Boxing Day purchases: it "does not apply to sleeping bags for children or babies". A comfort figure on a child's bag is the seller's number, not a lab one, and the only children's bag standard we found at BSI covers cot sleep bags. So treat that figure as a claim, not a measurement, and buy for a colder night than you would for yourself. The rest of the kit list is in our Bronze expedition packing guide.

The season label is not a standard

Season ratings are the shorthand British shops sell on, and there is nothing behind them: no British Standard, ISO standard or governing body defines the one-to-five scale. Criterion, a UK manufacturer, calls its own season ratings "an informal guide". OLPRO is blunter: they are "not tested to any universal standard. One brand's '3-season' might be another's '2-3 season.'"

The drift is measurable, and the two are not even quoting the same kind of number: Criterion's table puts a 2 season bag at 0 to +5°C and a 3 season bag at 0 to -5°C as plain temperature bands, while OLPRO's puts them at EN/ISO comfort ratings of 5 to 10°C and 0 to 5°C. A bag Criterion calls 2 season covers the band OLPRO calls 3 season. The labels cross over inside one catalogue too: Alpkit rates its Cloud Peak 300, a 3 season bag, at a -8°C limit and its Skyehigh 700, a 4 season bag, at -7°C.

Our review of the SWTMERRY bag, which says winter on the label and 5°C in the small print, ends in a rare leave-it: the title names four seasons while the bullets say "used for 3 seasons" and print a comfort range of 10 to 20°C. The MalloMe, sold as 3-4 season, prints a comfort range of 10°C to 25°C. The Voyager claims 3-4 season and quotes no comfort or limit temperature at all.

The label check, in order

  1. Find a temperature in degrees Celsius. Not a season count, an actual number. If there is none on the label, the listing or the brand's own page, you are buying a claim with nothing underneath it.
  2. Find the word comfort next to it. Treat a bare figure as the limit, so the temperature at which you sleep rather than endure sits several degrees warmer: five, on that Rab bag. The standard requires a label warning below the limit: "a strong sensation of cold has to be expected. There is a risk of health damage by hypothermia."
  3. Read the title against the bullets. Where a headline and a specification disagree, the specification describes the bag.
  4. Look for the standard by name. ISO 23537 or EN ISO 23537 means a laboratory figure exists. A number with no standard beside it is the seller's own estimate.
  5. Hold the comfort figure against where you sleep, and leave a margin. The rule runs one way: comfort below the coldest night you expect, with a few degrees spare. Met Office 1991-2020 averages put the mean December overnight low at 3.08°C at Heathrow, 1.85°C at Keswick and -1.07°C at Braemar, which averages nearly 100 days of air frost a year. Those are averages of the nightly minimum, so about half of nights are colder. An average December night at Keswick sits below that Rab bag's comfort figure, and its nine or ten December air-frost nights sit below the limit.
  6. Budget for what goes under you. ISO 23537-1:2016 runs the test with the bag lying on a foam mattress, and counts that "mattress underneath the sleeping bag" in the figure it produces. A bag on bare ground is not the bag that was tested, so an insulating mat is part of the purchase, not an extra: judge it by R-value, not thickness.
  7. Check the returns window before you pay. In a shop it is often shorter on sale stock.

Our view, plainly: for a bag you are buying to sleep out in the cold, no tested figure anywhere is not a bargain at any reduction, because you cannot know what you bought until the night it fails. A figure warmer than your coldest expected night is not a bargain either. If the budget only reaches an untested bag, buy it and know what it is: on a mat, with a liner and dry sleep layers, that is a July Scout camp bag, not a February one. Our own cold-night guide puts the ground first: that is where most of the heat goes.

Sale prices, was prices and what the law asks

Drop the rule you have probably heard: there is no 28-day was-price rule in current UK guidance. The CTSI Guidance for Traders on Pricing Practices, updated in April 2026 and referred to by regulators making enforcement decisions, does not contain one.

What it sets instead is a five-part judgement on whether a comparison price is fair, including how long the higher price ran, how recently it was charged, and whether the product is in demand for only part of the year. That last factor is the sleeping bag one: CTSI flags as less likely to comply a trader who "offers the product at a higher price when the product is out-of-season and then lowers the price in time for the expected product demand".

The Digital Markets, Competition and Consumers Act 2024 bans one practice outright: "Falsely stating that a product will only be available for a limited time ... in order to elicit an immediate decision". A countdown clock is not evidence of a saving.

Returning it: a shop and a website are different

In a shop there is no automatic right to a refund for a change of mind. Citizens Advice: "You don't have an automatic right to get your money back if you just change your mind about something you've bought and there's nothing wrong with it." Shops often allow 14 or 30 days as goodwill, GO Outdoors 28, but that is policy, and Citizens Advice notes it is often shortened on sale items.

Online is stronger. Under the Consumer Contracts Regulations 2013 you can cancel without giving a reason, and for goods the period ends 14 days after the day the bag reaches you. A second clock then runs: 14 days from telling the seller to send it back, with return postage on you by default.

Opening the stuff sack does not end that right: the test is whether handling went "beyond the sort of handling that might reasonably be allowed in a shop", and the trader may deduct for value lost past that.

If the bag is faulty or not as described, the Consumer Rights Act 2015 gives 30 days to reject it for a full refund, with the trader paying the reasonable cost of return. That clock starts the day after delivery, not the night the bag disappoints you.

What none of it covers is a bag that performs to its printed figure and is simply colder than the trip needed. Buy on 26 December, sleep out first in February, and all three windows above have shut: the check has to happen before you pay. Then unpack it in the first week and get in it indoors, checking the length, the zip and the loft while all three windows are still open.

Where this goes wrong

Buying the season number is the commonest error: informal by its own authors' description, and a full label apart between sellers.

Then there is buying the bag and stopping there. What is under you decides a cold night as much as what is over you, and on a tight budget a mat does more than a warmer bag.

Frequently asked questions

Is Boxing Day a bank holiday in 2026?

Not on the day itself in England and Wales. Boxing Day 2026 falls on Saturday 26 December, so GOV.UK lists the bank holiday as Monday 28 December.

What does the extreme rating on a sleeping bag mean?

It is a survival figure, not a usable one. ISO 23537-1 calls it the temperature where "the risk of health damage by hypothermia is possible", a point of danger "which can lead to death".

Does a was price have to have been charged for 28 consecutive days?

No such rule sits in current guidance. The CTSI pricing guidance, updated in April 2026, applies a five-part fairness judgement instead. One of its five factors is whether the product is only in demand for part of the year, which is exactly what a sleeping bag is.

Can I return a sale sleeping bag that is not warm enough?

It depends why. If it is faulty or the printed figure is wrong, sale items carry the same statutory rights as full-price ones, with 30 days from delivery to reject under the Consumer Rights Act 2015. If it simply was not warm enough for the night you took it on, that is not a fault: a shop owes nothing by law, and an online order can only be cancelled within 14 days of delivery. Both clocks shut long before a February camp.