When it comes to sleeping bags, temperature ratings are not an exact science. These ratings are not a guarantee of warmth, but rather a rough guideline to help you compare between different products. Sleeping bags don’t generate warmth; your body does, and the sleeping bag is designed to keep that warmth inside. With that in mind, every human body is different, every night is different, and there are many factors that combine to create a warm night’s sleep.

All Western Mountaineering bags have a temperature rating based on extensive field testing and fill weights, and these ratings rely on the use of a properly insulated ground pad (R 5.38), base layers and socks. We have EN testing data available for most of our models, and you’ll find the WM rating usually falls somewhere between the limit and comfort ratings derived from that testing protocol.

Tips to Stay Warm:

-Use a base layer; a dry light/midweight thermal layer can easily add warmth to your sleeping system, plus it will help shield your sleeping bag from body oils and grime, keeping it clean and extending it’s lifespan.

-A warm pair of sleeping socks and/or warm caps can go along way to stay cozy. The head and feet are major areas of heat loss, and covering up is an effective way to lock in your warmth.

-Stay warm and dry through the day. Maintaining a warm body temperature is crucial to keeping a consistent temperature as your sleep. Going to bed cold often makes it impossible to bring your core temperature up during the night.

-Calories. Without sufficient caloric intake, the body’s metabolism can fail to generate enough heat during the night to stay warm. Try a high fat snack before bed, or a hot cup of tea. Or try filling a Nalgene bottle with hot water and throwing it into your bag before zipping up.

-Sleeping pad: Always use a sleeping pad, and choose the appropriately insulated pad for the conditions you expect to face. A pad R-Rated between 3-5 is appropriate for summer use, while a 7+ R-Value is a good choice for winter and snow camping.