There’s not a year doesn’t go by where a family member or friend smugly sidles up to me and declares they have bought a sleeping bag from the local supermarket that can keep them warm down to -15 degrees.
Now if I don’t particularly like them I advise they they head off into the Scottish Highlands and really test this rating to the max. If I do like them I quietly enquire whether they have read the extreme temperature rating and not the comfort one….
So What Is The Extreme Rating?
The extreme temperature declared on sleeping bag is one of three temperatures that are called when sleeping bags undertake independent testing as part of EN 23537:2016. Basically sleeping bag are sent away to a lab, a temperature sensor manakin is placed inside and then the ambient temperature is lowered and readings taken. This in turn produces three temperature ratings which can be compared to other sleeping bags you may be looking at purchasing:
Comfort Temperature
This is the external temperature that a standard female can sleep comfortably in the tested sleeping bag and in a relaxed position. It’s worth noting that the manakin has base layers thermals on and is sleeping on top of an insulated sleep pad. The manakin also has the hood of the sleeping pulled tightly around their noggin. So if you don’t do all of these things when you go away camping that comfort temperature will be higher. If you were also wondering what a standard female is the lab people believe she is 25, 1.6 metres in height and weighs 60kg.
Lower Limit Temperature
This is the external temperature that a standard male can sleep comfortably curled up in the tested sleeping bag. It’s usually a few degree lower than the comfort temperature as men generally sleep warmer than women due to body mass and circulation differences.
Extreme Temperature
Finally the one we are here to talk about! This is officially classed as the minimum temperature that someone can sleep in this sleeping bag without getting hypothermia. One enormous note here in the test is that it’s likely that the user may get frostbite and lose a finger or two!!
Ignore the Extreme Temperature
We understand that this temperature is created to advise expedition leaders as to whether their kit can withstand worse case scenarios but for the average camper or backpacker it’s a dangerous thing to print on a sleeping bag. That’s why we don’t even include it on our specifications section because we think it can cause more confusion and lead to the risk of a terrible nights sleep. We always advise our customers to take note of the comfort temperature and then search on Google for average night time temperatures at their chosen camping spot. Alternatively if you always feel the cold grab yourself a 5 season sleeping bag!