Toasty Tips for a Warmer Sleep

Is your sleeping bag failing to keep you warm during the winter months?

Do you remember it being…warmer? Does it seem to have lost its warmth over the years?

Maybe you have a sleeping bag that’s better suited to the summer months, you’re about to head out in winter, and don’t want to buy another sleeping bag?

If this sounds like you, this blog lists 5 toasty tips for a warmer sleep – but first, let’s bivvy down and learn a little more about the humble sleeping bag…

Sleeping a sleeping bag next to dog

Brrrr, winter camping can get positively arctic if your sleeping bag isn’t warm enough! Credit: Sea to Summit 

The Sleeping Bag

Sleeping bags are one of the only products on the market that have a temperature rating. Think about it, it’s not common to buy a jacket or even a quilt for your bed at home with a temperature rating.

As a general rule, if we feel cold we put an extra jumper on or another blanket on the bed. Despite this, we expect that a sleeping bag with a ‘temperature rating’ of 0 degrees will keep us toasty warm in the snow, no matter what type of person we are.

The reality is that this temperature rating is only a guide. We all feel the cold differently, so we simply cannot expect a sleeping bag to reflect such science – or that one temperature rating fits all.

So, what does temperature rating mean? How can we use this roughly equated number to help us choose an appropriate bag for the job?

A lady in a beanie sitting in her tent, snuggled up in a sleeping bag.

We all feel the cold differently. Credit: Sea to Summit

Sleeping Bag Temperatures

Before delving in – ask yourself:

  • Do you usually go camping during cold weather, when it’s warm, or both?
  • If the weather is forecast to be cold – how cold? Is there a chance of frost or snow?
  • Are you sleeping outside, or in a tent? How large is the tent? Is it just for sleepovers?

With those considerations in mind, let’s talk sleeping bag ratings:

+5 to +10-Degree Bags

+5 to +10 is considered a ‘summer’ bag. It is roughly as warm as sleeping with a sheet or light blanket on your bed at home.

0-Degree Bags

0 degree bag is a great all-rounder, but won’t keep you warm in the snow or frost – it’s about the same as having a regular doona on your bed at home.

-5 to -10-Degree Bags

A -5 to -10 degree bag is considered a ‘winter’ bag for typical Australian climates – it should be similar to having flannelette sheets and an extra blanket or two on your bed at home.

Choosing Your Sleeping Bag

The temperature rating is the point at which you will likely wake up to. You will feel cooler as the external temperature approaches this rated temperature, so it’s important to allow yourself a temperature buffer. The below factors are worth considering to help select the right bag for you.

  1. First, determine the lowest temperature you will be using the sleeping bag in most of the time.
  2. From here, we recommend adding a buffer to ensure you sleep warm. This is dependent on how you sleep:
    • Warm sleepers: refer to the EN/ISO tested ‘Comfort’ rating as a starting point, and choose a bag with a rating at 5 degrees below the lowest temperatures you plan to use your sleeping bag in.
    • Cold sleepers: refer to the EN/ISO tested ‘Lower Limit’ rating as a starting point, and choose a bag with a rating at 5-10 degrees below the lowest temperatures you plan to use your sleeping bag in.
  3. Keep in mind that you can expand the comfort range of a sleeping bag by adding liners for extra warmth, or use the sleeping bag unzipped as a doona to cater for temperature extremes you may occasionally encounter.
  4. Finally: this is not an exact science. We are all different, with varying metabolisms. You’ll need to use some of your own judgement in your selection.

A lady in a beanie sitting in her tent, snuggled up in a sleeping bag.

You will feel cooler as the external temperature approaches the sleeping bag’s rated temperature. Credit: Sea to Summit

EN/ISO Temperature Rating

Sleeping bags must be independently tested by the manufacturer to obtain this rating. The rating is often based on an R-value, which is a measurement of insulation – just like the insulation in the walls of your house.

Some manufacturers will do real world testing on one sample of their insulation, and apply a formula to the different sleeping bags. On the other hand, sleeping bags tested to an EN (European) Standard (or an ISO or international standard as of 2016), are the most accurately tested bags.

That said, keep in mind that this testing is done in a controlled and static environment where a dummy is placed inside the sleeping bag with temperature sensors. So, unless you’re a motionless dummy sleeping in an environment void of variables, you’ll need to allow for your own physiological makeup and the equipment you are using.

What is the EN or ISO Standard?

There are no testing guidelines here in Australia, so look out for bags that have been tested according to EN Standards. The EN Standard for sleeping bags is marked EN13537, which was superseded by the ISO 23537-1 international standard in 2016.

The standard measures three temperature ratings:


The temperature at which a standard woman can expect to sleep comfortably, without feeling cold and in a relaxed position.

Lower Limit

The temperature at which a standard man inside the bag sleeping in a curled position is starting to feel cold, but not shivering. This is the limit of performance for the sleeping bag.


At this temperature, anyone can expect to feel particularly cold with a risk of hypothermia. You should only use the sleeping bag in this range for an emergency.

A man in a beanie holding a thermos, snuggled up in a sleeping bag.

Look out for bags that have been tested according to EN Standards. Credit: Sea to Summit

Not all manufacturers will list all three ratings – ensure you’re considering the correct one. Ultimately, no amount of laboratory testing is going to be 100% accurate to your body. Less expensive sleeping bags will advertise a more generous rating that may not be accurate. Bags that list the EN/ISO Standards will be more accurate and provide a good point for comparison between bags. As that process is expensive though, it will affect the price tag.

You can always shed a layer or unzip your bag if you’re hot – but if you wake up freezing cold in the middle of the night, there won’t be much you can do to get warm!

On that note, below are five ways to improve the warmth and therefore quality of your sleep on those colder camping trips:

1. Wash Your Sleeping Bag

If your sleeping bag is on the ‘well-used’ side and doesn’t seem to be as warm as it once was, you may need to simply give it a good wash. Over time, the oils from your skin together with moisture caught in the filling can cause the stuffing to clump together. This prevents it from ‘fluffing up’, which keeps you insulated and warm.

The filling in the sleeping bag needs to ‘puff up’ and expand with air, which then traps the body heat of the person sleeping inside. Washing your old sleeping bag will clean the filling and enable it to do this more effectively, thus trapping more warm air and increasing the insulation between the person inside and the cold air outside.

An open washing machine that contains a sleeping bag and 3 tennis balls

Wash your sleeping bag to restore its warmth. 

How to Wash Your Sleeping Bag:

  1. Put your sleeping bag in a pillowcase to protect the thin outer material from tearing.
  2. Using a front loader, wash your sleeping bag on a warm, gentle cycle (if you have a down sleeping bag, use Down Wash).
  3. Dry your sleeping bag in a large tumble dryer on the lowest setting. Place a few tennis balls inside the dryer too; these will smash into the sleeping bag, breaking up the filling and fluffing it up again.
  4. If you don’t have access to a dryer, simply dry the sleeping bag on the clothesline in the sun. Every half an hour or so, beat it with a tennis racket to break up the filling.

A woman lies in her tent in a thermal liner and sleeping bag, reading a book

In an ideal world, you would have a sleeping bag for every season. But in reality, you can make one sleeping bag a lot more versatile with a few of these hacks. Credit: Sea to Summit

2. Thermal Liners and Hot Water Bottles

Thermal Liners

If your sleeping bag isn’t rated low enough for the conditions you’re using it in, or if you’ve discovered you’re a cooler sleeper – rather than purchasing another sleeping bag, consider adding a silkcotton, or fleece liner.

thermal liner is made of the same material as thermal underwear, specifically designed and rated to boost the warmth of your sleeping bag. While there are many on the market, the cotton and silk liners by Sea to Summit are a personal favourite.
By adding a liner to your bag, you not only have a sufficient winter sleep system but can still use the sleeping bag on its own in average conditions. The liner can then be used on its own in warmer weather! A removable liner also keeps your sleeping bag cleaner, and thus your filling in better condition.

On the contrary, avoid adding extra blankets on top of your bedding. The weight will crush the filling, rendering it ineffective for trapping the air. Use them beneath you, or under your mat instead.

Hot Water Bottles

If you’re heading away for a particularly cold weekend, it may be worth packing a good ol’ fashioned hot water bottle too. You can also use a regular water bottle – just ensure it has a quality seal so it won’t leak, and the water inside isn’t too hot. Sports-style bottles aren’t usually a good idea, but the Nalgene, 360 Degrees Stainless Steel drink bottles and those alike work well.

Heat the billy before bed and pour the hot (not boiling) water into your bottle. Tuck it into your sleeping bag with you – and enjoy some seriously snug comfort! Better yet, if you prepare it ahead of time, you’re pre-heating your bed so it’s warm by the time you officially hit the sack!

A man wearing a beanie and thermal top sits up in his sleeping bag inside a tent

Layer thermals under your clothes while you sleep. Credit: Sea to Summit

3. Thermal Clothing

Thermal underwear are the warmest pyjamas you will ever need when camping in cold conditions! Known as a ‘base layer’, they will trap warmth directly against your skin and make a huge difference to your comfort in cold conditions. Layering clothes on top of your thermal base will trap air between the fabric, keeping you warmer than simply adding a single thick layer of clothing.

Ensure you add your layers and warm up by the campfire well before lights out too, so the heat has time to build. This will also have it easier to maintain, as it will be trapped with you when you slide into your sleeping bag.

A man lies outside in a sleeping bag, wearing a beanie and heating a kettle on a hiking stove

Keep your extremities warm on a cold winter’s day. Credit: Sea to Summit

4. Beanie and Socks

Humans lose about 30% of their body heat through their heads! By wearing a beanie to bed or tightening the hood of your sleeping bag, you’re trapping more warmth. Simply keep your mouth and nose free so you’re not breathing into your bag – this creates moisture throughout the night.

When your body becomes cold, it takes blood from the extremities such as your feet and hands to instead keep it surrounding your vital organs. By heading to bed with warm socks and gloves, you’re keeping your feet and hands warm, which maintains the blood flowing to them. This makes for a better night’s sleep!

A woman preps food on a table next to a river

Tuck into a large dinner before bed. Credit: Coleman

5. Eat a Big Dinner!

Your body uses a lot of energy to digest big meals. In the case of a large dinner, all this energy will produce heat and keep you warm come bedtime. By eating a decent sized dinner packed with low GI carbohydrates, your body will continue to burn fuel all through the night!

Two-minute noodles give you enough energy for… well, two minutes. On the other hand, a big bowl of spaghetti Bolognese will ensure a good night’s sleep! Just don’t eat too much…and go easy on the garlic, or you’ll be awake with indigestion! Contrary to popular belief too, if nature calls during the night you are better off surrendering to it; holding on will override your kidney’s signal to your brain. Through a chain of technical temperature regulation measures, our bodies feel colder when our bladder is in need of relief!

A couple in their sleeping bags inside an open tent

Hopefully, this advice will help keep you snug while you sleep. Credit: Sea to Summit

Keep Warm on Your Next Adventure!

No matter the age or quality of your sleeping bag, these tips will help you achieve the best from it.

It’s worth noting too that your sleeping bag is part of a whole sleep-system. This means that your choice of sleeping mat will also influence how cold or warm you will be throughout the night.

An airbed is not one to keep you warm, as the air within the mattress will remain cold. Instead, choose a closed-cell foam or filled mat, which traps air and helps insulate. Sleeping inside a smaller tent that is double-walled (ie. using a fly) and having decent ventilation to reduce moisture build-up are also tips worth bearing in mind.

Here’s hoping you can get a good night’s sleep, even on those freezing cold winter nights! With the above tips, you’re less likely to resort to the dangerous (and not recommended) tactic of using a heater inside your tent… or to the ancient Native American method of creating a hot rock bed!

Two Sea to Summit sleeping bags in a tent, looking out to two campers by the fire.

Your sleeping bag is part of a whole sleep-system. Credit: Sea to Summit

Do you practice any of these tricks? Got any more to add? Comment below.