King of the Mountain offers many different systems. They literally make garments capable of keeping you toasty in an artic tundra. Their lighter garments designed for bow hunting and all day sits in less freezing circumstances are amazing though. You can sit in 10-30 degree weather all day and be just a little too warm. LOL. Very, very expensive but for people really affected by cold, it is a great option. I like to hunt late season a lot and these garments have never let me down. I don't wear them if I plan on doing a lot of moving though.
You want me to put my ear to the ground? Listen for hoof beats? Look for broken twigs?