Last updated: June 2026
Temperature
A few years ago, my younger daughter and I both packed sleeping bags advertised around 0°C. Mine was a Marmot Never Winter. Looking at the weather, it seemed like the right choice.
The lowest recorded overnight temperature in Banff in August over the last two years was -1°C.
The difference between 0°C and -1°C didn't seem significant.
So why were we cold almost every night?
The answer is the comfort rating.
My Marmot Never Winter is marketed as a 30°F (-1°C) sleeping bag, but its comfort rating is around +5°C.
The comfort rating is the temperature at which an average adult woman is expected to sleep comfortably. The lower-limit rating is based on an average adult man. If you know that you tend to sleep cold, the comfort rating is the better number to use when choosing a sleeping bag.
Meanwhile, my oldest daughter used a -8°C sleeping bag and slept comfortably every night.
What if a sleeping bag does not have a comfort rating?
Not every sleeping bag lists a separate comfort rating. Many bags only show a limit rating or a printed temperature on the tag.
This matters because the limit rating is usually closer to the temperature where an average man can sleep without excessive cold. It does not necessarily mean that the bag will feel comfortable for everyone at that temperature.
For women, or for anyone who sleeps cold, it is usually safer to treat the printed limit rating as too optimistic. If a bag does not publish an official ISO or EN comfort rating, I would generally add about 5°C to the printed rating to estimate a more realistic comfort temperature.
Example: If a sleeping bag is labeled 0°C but does not list a comfort rating, I would treat it more like a +5°C comfort bag.
If the lowest overnight temperature is close to freezing, that bag may not be warm enough for someone who sleeps cold.
If the manufacturer provides an official comfort rating, I use that number first. If they do not, I treat the printed rating as a lower-limit number and build in extra warmth.
Want exact sleeping bag recommendations?
The best top 3 sleeping bags depend on your trip dates, overnight low, gender, pack size, comfort rating, weight, and compressed volume. For exact recommendations based on your own trip, use TrailReady.ca.
Comfort rating vs. printed rating
This is the main reason a sleeping bag can look warm enough on paper but still feel cold in Banff. The printed number is not always the comfort rating.
| Printed rating | Comfort or estimated comfort | For a +1°C Banff low |
|---|---|---|
| +5°C comfort | +5°C | Usually too cold |
| 0°C printed limit | About +5°C estimated comfort | Usually too cold for women or cold sleepers |
| -5°C printed limit | About 0°C estimated comfort | Better, but still close |
| -7°C comfort | -7°C | Good warmth margin |
For exact top 3 sleeping bag recommendations, go to TrailReady.ca.
TrailReady uses your destination, trip dates, expected overnight low, comfort rating, weight, compressed size, and gender-specific warmth needs to rank sleeping bags for your trip.
Weight
On a seven-day trip, you're already carrying several kilograms of food. Every extra gram matters, especially on long climbs.
Compressed size
Compressed size is just as important as weight.
Seven days of food occupy a surprising amount of backpack space. A sleeping bag that compresses well leaves more room for food and makes packing much easier.
That's one of the reasons I prefer down sleeping bags. They usually compress much smaller than comparable synthetic bags while also weighing less.
When comparing sleeping bags, look for the manufacturer's Packed Size, Stuff Sack Dimensions, or Packed Volume. These specifications tell you how much space the sleeping bag will occupy inside your backpack.
For example, a packed size of 18 × 36 cm corresponds to roughly 9 litres of backpack space. In a 55-litre backpack, that's about 17% of the available volume.
As a rule of thumb, I try to keep my sleeping bag under 15–20% of my backpack volume, especially for trips lasting a week or longer.
What else matters?
Sleeping pad
Your sleeping pad insulates you from the cold ground. For temperatures around freezing, I would use a sleeping pad with an R-value of at least 4.
| Lowest overnight temperature | Recommended minimum R-value |
|---|---|
| Above 10°C | 2–3 |
| 5°C to 10°C | 3–4 |
| 0°C to 5°C | 4 |
| Below 0°C | 5+ |
Sleep clothing
I also keep a dedicated set of clothes just for sleeping:
- Warm base layers
- A warm hat
- Dry wool socks
- Lightweight gloves when cold nights are expected
Changing into dry clothes before bed makes a noticeable difference after a long day on the trail.
FAQ
What temperature sleeping bag do I need for Banff in August?
Use the lowest expected overnight temperature, then compare it to the sleeping bag's comfort rating. If the lowest overnight temperature is close to +1°C, many people will be more comfortable in a bag with a comfort rating below freezing, especially if they sleep cold.
Is a 0°C sleeping bag warm enough for Banff?
Not always. A 0°C printed rating may be a lower-limit rating, not a comfort rating. If the comfort rating is +5°C, the bag may feel cold when the overnight temperature is near freezing.
What if the sleeping bag does not list a comfort rating?
If there is no official ISO or EN comfort rating, treat the printed temperature as a lower-limit number. For women or cold sleepers, adding about 5°C gives a more realistic comfort estimate.
What sleeping pad R-value do I need for Banff?
For temperatures around freezing, I would use a sleeping pad with an R-value of at least 4.
About the Author
Ioulia is the founder of TrailReady.ca, a backpacking trip planner that recommends gear based on destination, weather, trip duration, and hiking conditions.
For the past several years, she and her family have completed backpacking trips in Banff National Park. The advice in this guide is based on those trips and the lessons learned from choosing and testing backpacking gear in real mountain conditions.