"Coldest" Black Metal Band?

I suppose it depends on what you mean by "cold"

I'd have to go with Immortal and Xasthur (subliminal genocide)
and darkthrone of course.
 
Blizzard Beasts - Definitely!

Battles in the North also, but Blizzard is far colder.

Truely, Immortal are so cold, I can't listen them in the summer time. It is just strange. I can't imagine how people listen Immortal in Mexico or Brasil. It's just weird. :)

There are 97 Inuit words for Snow. Immortal has 98.
 
Immortal, but it depends on what you go by.
Immortal was cold production wise, but on their more recent albums,the coldness is mainly in their lyrics and music itself, with a little bit from the production.

Nothing too cold about Burzum, but Darkthrone is another cold sounding band.

Immortal is my favorite black metal band, though.