Manufacturers nowadays seem to claim about anything. 4-season means SNOW. Snow presents different problems - 1) weight of snow on the tent, 2) snow blowing in the tent, 3) frosting up and condensation and 4) room. A winter tent has to have a steep enough pitch that snow will slide off and also the poles have to be strong enough to hold a snow load when it does not sluff off easily. Blowing snow means you have to be able to buttom up the tent and not have spindrift come in. This is also handy in desert areas with blowing sand. This usually means nylon windows that zip up over the mesh. Frosting is usually solved by a bigger tent. In the winter, you need more room anyway to accomodate bulky down clothing. You also need to store boots and gear inside. In serious winter mountaineering 4-season tents you actually have a double entry - get in the vestibule, close it up, shake off the snow, then get in the real tent. The vestibule also is handy for cooking without getting snowed on. ALso if you have to hole up for a storm, a tiny tent is really uncomfortable. All said, it is hard to get a real winter 4-season tent under 4-5 pounds. 4-Season also means the tent has to suffice for summer. Thus, there are some winter tents that do not do well in summer. You will usually carry too much around having a 4-season tent for summer. Most 4-season backpack tents really are only designed for the shoulder seasons. They are seldom true winter tents. If you do snowy winter backpacking you probably would be better getting a specific tent for winter.