In the world of mountaineering and cold-weather "sleepovers", shelter means more than just warmth, it often means life. The trend of the convertible (a four season tent with ventilated panels or windows that can be secured shut to prevent spindrift from getting inside a tent, more rigid pole structures, dual entrances with vestibules to increase ventilation flow-through, etc.) continues to gain design popularity.

However, this trend toward all-weather compromise has spawned the need for what is termed a "fifth season" shelter. These shelters are designed for hard-core, mountaineering / extreme weather use with no compromises, no shaved corners-call it the expedition tent and a growing number of companies including Sierra Designs, VauDe, The North Face, Marmot, Mountain Hardwear, Moss, Walrus, Wild Country and Quest make a point of differentiation.

Like their convertible cousins, the expedition tents offer versatile features but they also turn to larger diameter aluminum poles (most often Easton), lower profiles, increased and more judicious use of guy points, and stronger, more wind-resistant fabrications. All of these additions translate into higher costs ($500 and up), but also far greater weight to strength ratios and structures that really can hold up in 100 mph winds.

The most interesting note in the realm of convertible and fifth season tent design of late is found in the design communication inspired by the fear of litigation from liability. Both convertibles and fifth season tents offer what manufacturers refer to in one breath as "a vestibule large enough for storage and cooking." However, these same manufacturers unanimously modify their assertion in the next breath by stating "of course we don't ever recommend cooking in a tent since it is so dangerous." As any serious mountaineer knows, when its a snowin' and blowin', cooking in the tent is not an option, it is a matter of survival.