Temperature Guide
Bosideng Warmth Guide
Everyone experiences the cold differently. Our Warmth Guide is designed to help you choose down outerwear for the conditions you will actually be wearing it in, from a mild spring evening to a long day outdoors in deep winter.
Each style is assigned one of seven Warmth Levels, based on how the garment is built rather than on a single number. You will find the Warmth Level on every down product page.
The Scale
Seven Warmth Levels
Each level shows a recommended temperature range for everyday wear. Neighbouring ranges overlap on purpose: the right choice within an overlap depends on how long you will be outside, how active you are and how you layer.
Warmth Guide
The scenarios below are examples to help you picture each level. They are a starting point, not a limit.
Level 0
+10°C to +20°C50°F to 68°F
Minimal protection
Designed for
Spring and summer conditions. A lightweight outer layer that offers wind protection and sun coverage, with little to no insulation.
Typical scenarios
Breezy spring days, summer evenings, travel and holidays where a packable layer is useful.
Level 1
0°C to +10°C32°F to 50°F
Transitional insulation layer
Designed for
Transitional seasons and layering. Light insulation for mild and changing conditions.
Typical scenarios
Autumn and early spring, cool mornings, wearing indoors, or as a mid-layer under a shell or a warmer coat.
Level 2
−10°C to +5°C14°F to 41°F
Light chill defence
Designed for
Cool weather. Reliable warmth for early winter and cold city environments.
Typical scenarios
Daily commuting in late autumn and early winter, city walks, short waits outdoors on chilly days.
Level 3
−20°C to −5°C−4°F to 23°F
Cold weather shield
Designed for
Cold winter conditions. Dependable insulation for daily wear in sustained cold.
Typical scenarios
Midwinter commutes, longer periods outdoors in freezing weather, winter city breaks to colder destinations.
Level 4
−30°C to −15°C−22°F to 5°F
Severe cold protection
Designed for
Severe cold and prolonged outdoor exposure, where enhanced insulation is needed.
Typical scenarios
Deep-winter travel to northern regions, extended time outdoors in harsh cold, après-ski and winter sightseeing.
Level 5
−50°C to −30°C−58°F to −22°F
Ultra-cold protection
Designed for
Extremely cold conditions, using enhanced insulation and construction. Intended for specialised use rather than everyday city wear.
Typical scenarios
Travel to sub-arctic regions in winter and long periods of low activity in intense cold.
Level 6
−60°C to −50°C−76°F to −58°F
Ultimate Polar Protection
Designed for
Extreme and polar environments, offering our highest level of insulation and protection.
Typical scenarios
Polar and high-latitude environments. Reserved for a small number of dedicated styles.
Our Method
How we assign a Warmth Level
Warmth comes from the whole garment, not just one specification. We look at the following together when rating each style, and we deliberately take a conservative view.
Down type
Goose down and duck down have different cluster characteristics, which affect how they insulate.
Fill power
Fill power indicates how much loft the down provides. Higher fill power traps more warm air for the same weight of down.
Fill weight
The amount of down in the garment. Together with fill power, it determines how much warm air the insulation can hold.
Length and silhouette
Gilets, jackets and longer parkas cover the body differently, which changes how warm they feel in the same conditions.
Shell fabric
Wind-resistant and water-resistant outer fabrics help the insulation keep its warmth in real outdoor conditions.
Lining and construction
Heat-retaining linings and protective details such as hoods and higher collars are also taken into account.
Your Comfort
Why your experience may differ
Temperature ranges are a guide. How warm you feel on the day also depends on:
Individual perception
Some people naturally feel the cold more than others. If you tend to feel cold, consider the next level up.
Layering
What you wear underneath makes a real difference. A warm mid-layer can extend the range of a lighter coat.
Activity level
Walking briskly generates heat; standing still at a bus stop or watching an outdoor event does not.
Wind and humidity
Wind and damp air can make conditions feel considerably colder than the temperature on the forecast.
Time outdoors
A ten-minute walk and a full afternoon outside call for different levels of warmth.
Fit
A fit that leaves room for layers, without large gaps at the hem and cuffs, helps keep warm air in.
FAQ
No. The Warmth Level is a recommendation to help you compare styles and choose for your typical conditions. Because comfort depends on the person, the layers worn, activity and the weather on the day, we cannot guarantee how warm any individual will feel at a given temperature.
The hang tag reflects laboratory testing under controlled conditions. Our Warmth Guide is an everyday-wear recommendation that takes the garment's construction and real outdoor conditions into account. Both are valid references; they simply serve different purposes.
There is no single point at which one level stops being suitable and the next begins. Within an overlap, choose the warmer level if you feel the cold easily, expect to stand still for long periods, or will be outside in wind; choose the lighter level if you will be active or plan to layer underneath.
For winters where daytime temperatures are usually a little above or around freezing, Level 2 (Cool) suits most daily wear. If you spend long periods outdoors, feel the cold easily, or are heading somewhere with regular sub-zero temperatures, consider Level 3 (Cold).
We take an even more conservative approach when rating children's styles. Please check children regularly in cold weather, as they may not always say when they are cold.
These levels are designed for very cold conditions, but a coat is only one part of the equipment needed for high-risk activities. For expeditions, mountaineering or professional use in extreme environments, please seek specialist advice on your full clothing and safety system.
Need help choosing?
Tell us where and how you will wear it, and our team will be happy to recommend a style.