I've had a request for apples trees from someone in south eastern B.C. She
says her area is zone 4 - a brief chill of -30 to -35°C for a week each
January
with ample snow cover - more than 3'. I think that's about -20 to -30 °F.
Del would that be you?
I just need to advise her what varieties would survive those temps and what
rootstocks are suitable.