Viscose yarn actually behaves quite a bit like cotton, as it's very absorbent and breathable. This along with its lightweight characteristic and hardiness makes it a great fabric for warm weather wear. Since it's so cheap to produce, it's cheap to the consumer, as well, but it won't be very helpful for people who are concerned with staying warm, because it does not insulate well. People who live in warmer areas will find viscose is their best friend, but people who live where there are harsh winters and mellow summers, or people who are more concerned with the environment, may use this fiber less.

http://www.seagorcare.com/viscose-yarn/