I lived in Montana for 4 years and took some dandy whitetails there. Three different buck I shot were from stands when the temperature was -10 or more. This cold thing is relative. If your from an area that it gets cold every year then single digits wont make the deer lay down. In my experience they get more active. Somebody on this board has to be from the Alberta or Sas areas. They don't even like to hunt until they hit the single digits or below.