It's all about layers, I use the high tech underwear (HH or Underarmour) to keep moisture off the skin, then several layers to keep in heat and something to break the wind, also hand warmers and toe warmers help, in severe temps I use a Body Heater suite, it's a little cumbersome in the stand but it'll buy you a couple of hours. I learned the hard way a few years ago in very cold temps (-25C) that I had too many bulky players on, went to draw back on a buck and had such a hard time he stood there and watched me struggle then trotted off