Sleeping bags are often rated based on seasons, but there are several reasons why this isn’t a particularly accurate way to pick your bag.
The common terms you’ll hear are 2-season, 3-season and 4-season. These terms are about as accurate as the conditions you’ll face in these seasons.
For most UK camping a 3-season bag rating will be about right. This kind of sleeping bag should keep you warm enough at the chillier ends of spring and autumn without turning you into a boil-in-the-bag meal in summer. Tricks like using a liner when it’s cold or opening the zip when it’s hot make a 3-season bag good for most of the year.
The other ratings, however, can be somewhat misleading.
The 4-season rating is one with an obvious flaw - a bag that's warm enough in the depths of winter will be like sleeping in the oven in summertime in the UK. If you’re planning to use a 4-season bag to sleep out in typical UK conditions then save it for your snow holing trip to the Cairngorms.
For travelling further afield though then a bag like our SkyeHigh 700 or 900 would be suitable in the summer. If you’re trekking in the Pyrenees or bivvying in the Alps to get that vital early start then a 4-season bag is what you’ll need for a good nights sleep.
For winter trips to places like this though then you’re looking at an even beefier expedition bag like one of our ArcticDream series.
A 2-season sleeping bag rating is again a bit off the mark. These are the lightest, most packable bags going. They’ll use high tech fabrics and wafer-thin layers of insulation to keep weight and size down to a minimum. These bags say 2-season but even in summer you might find yourself feeling a little chilly.
If you were cycling around the Mediterranean in July then they would probably be fine with a Pipedream 400, but even in summer, the night time temperatures in the UK can be on the cooler side of comfortable.
These bags are aimed at the more extreme user to provide some vital extra warmth without the weight penalty. Think hardcore alpinists shivering on little mountain ledges or mountain marathon runners that think cutting their toothbrush in half is going to save them vital minutes on race day. These kinds of people love bags like the Mountain Ghost and PipeDream 200 because of their tiny size and weight, not their suitability for snuggly lie-ins.