I grew up 70 miles NW of Yellowstone. In SUMMER I remember arising for breakfast at 0500 then heading off for chores at 0630 I was wearing a lined leather jacket.
Seeing my breath. Water from the hand pump was so cold I curled my lip under so the temperature shock would not take it out on my front teeth.
You might want to think about the furnace fan draw unless your family is cold weather folk. I don't remember too many times where I ended up not having to tie my leather jacket onto the saddle around ten AM. Obviously I did not carry a thermometer around :)
