This is a very broad question. The very best od strain is the one that better suits your climate and your taste/needs. Take a look at this useful thread:
I would go with Mr nice super silver haze,serious kalimist, MR nice mango haze.oh and i like sativas .so if your a indaca lover i would not know . or do you like hybrids like a 70/30 or a 60/40. good luck
If u really want kick ass outdoor strains which I KNOW grows extremly well over there.. gp for Hybrids from Hell (dk seed comp.).. or look at seedbay for DK plants or try Zen seeds.com.. womderfull early stuff fro Dk.. or try Bluehemp .. got some great strains like Dark Kush.. Red Lebanon.. Chilla.. just my 2 cents...
I've attempted to grow outdoors many times where I'm at and have a hard time, that said I've had good luck with Herijuana outdoors, but they don't finish till mid-October so it depends on the year. I don't always have that long before things freeze up
hybrids from hell or breederbrad on seedbay should have something they grow in canada so it should finish eary
look up guerrilla gold specifically they might be what you need