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Season & Temp Ratings

A cozy and restful night's sleep while camping is the number one priority for most campers so selecting a sleeping bag most up to delivering that is an essential decision. However, it can all be a bit bewildering with various terms such as 'comfort rating', '4-season', temperature rating' and 'extreme temperature rating' bandied about like we all know what they mean.

In general, each of these ratings is designed to give us an indication of the upper and lower air  temperature limits in which the bag would be comfortable to sleep in but until relatively recently this was all a bit hit and miss. For starters, it is widely accepted that women sleep much colder than men. Additionally, each manufacturer carried out their own set of tests with no standardisation meaning that one maker's rating although identical to another's, didn't provide the same insulation. Ratings were guess work at best.

However, since the introduction of the European Norm testing methodology (EN), European  sleeping bags of any quality will carry an EN rating. This rating is carried out in independent, specially certified laboratories to provide an industry standard which gives the buyer a far more accurate and reliable way of comparing products. The US market has no such standardization although several of the leading manufacturers of sleeping bags have adopted the EN rating system.The EN method recognises the differences between the temperatures of men and women while they sleep and the terminology employed by their ratings relate directly to this. EN ratings are in Fahrenheit. EN ratings are based on the assumption that the user of the sleeping bag will be wearing a hat, one base layer of clothing and also using a sleep pad.

Comfort Rating

This rating  indicates the lowest temperature in which the average person could be comfortable sleeping with the sleeping bag in question.  So a +10 comfort rating means the average person could sleep comfortably in temperatures as low as 10 degrees Celsius. Due to the differences between men and women (women feel the cold more) many manufacturers give a range a temperature range for comfort.

Extreme

This rating is not intended for normal sleeping situations. It is a worse case scenario/survival rating which tells the buyer the extreme lowest temperature in which the bag would assist with enough warmth for survival. It has no relevance to comfort.

 

Season Ratings

Luckily, where sleeping bag season ratings are concerned the explanations are actually quite simple. Sleeping bags are sold with 1,2,3,4 or 5 season ratings and this refers to the minimum temperatures in which the bag can comfortably be used (hence the alternative term of  'comfort rating'). Be advised that where there is no EN endorsement, these ratings are a guideline only and will vary considerably from manufacturer to manufacturer.

 

One season sleeping bags are the lowest end of the scale. These bags are generally used indoors or in tropical climates. They are lightweight and compact and used by travellers.

Two-season sleeping bags are the base minimum for most campers and are sometimes known as summer bags. If you are not prone to the cold you may be able to use a two-season bag for the latter end of spring and the early part of autumn as well as in the summer. Typically sold as a sleeping bag which can be used in temperatures down to 5 degrees centigrade.

Three-season sleeping bags are the most common choice for experienced campers. Suitable for all but winter camping these sleeping bags are designed to keep you comfortable in temperatures down to around 0 degrees centigrade.

Four-season sleeping bags, as the name suggests, are designed for those who will be camping all year round or are likely to be in harsher environments such as camping at altitude in the mountains. Temperature range for four-season bags is around the -10 degrees centigrade mark.

Five-season sleeping bags are not really designed for the general market but are more usually associated with expedition standard camping requirements as they are suitable for temperatures down as low as -40 degrees centigrade.

 

Other Considerations

You don't need to be a scientist to know that people react very differently to the cold – what is chilly to one person would be unbearable for another. Season ratings are a great starting point but they are not an exact science. This is even more obvious when you realise that season ratings vary considerably between brands with the result that one make of two-season bag may actually be a warmer buy than another's three-season product.

Also consider the following:

  • those of a slighter build will not only have less body fat to keep them warm but will also leave more empty space in their sleeping bag which affects insulation and warmth
  • young people are less prone to the cold than older people
  • fitness levels will also dictate to some degree how much you feel the cold – usually the fitter you are the warmer you will be
  • typically men feel the cold less than women
  • where your tent is pitched and the environment generally may affect how warm you will feel – a tent pitched at altitude, somewhere exposed to the elements or in a damp place will all make you feel colder
  • your sleep mat – no matter how super-duper your sleeping bag, you are going to get cold if you don't insulate yourself properly from the ground

 

There is perhaps some degree of trial and error with regard to knowing which season sleeping bag will suit you best. Don't be too concerned about how hot you might get - sleeping bags can be unzipped or discarded altogether and getting cooler is always going to be easier than getting warm enough. Consider when and how you will be camping along with your own tolerance of the cold and then opt for the best sleeping bag your money can buy. As you snuggle down into your cosy sleeping bag on your next camping trip then you will be glad you invested both the time and money to find the perfect sleeping bag.