A temperature rating is a guide, not a promise. It describes an average person, rested and fed, wearing the piece as part of a system.
01Comfort
The comfort figure is the lowest temperature at which most people can stand still without feeling cold. We test ours at camp, in the evening, after a full day of walking.
02Active range
Moving produces heat, so the same jacket works in much colder air while you walk. The active range on our product pages covers that.
03What changes the number
Wind takes heat away quickly, so minus five in a gale feels like minus fifteen. Altitude, tiredness and an empty stomach all make you colder. If you know you run cold, add five degrees to any comfort rating.
The weather guide on our home page turns a forecast into a set of three layers. Use the coldest temperature you expect, not the average.