I cant give you specific to your question but Ive been to the okanogan and it sure is sunny and hot there! Probably the best place to grow weed in canada, problem is your going to have to water often. Look into something that retains moisture... I cant remember what its called unforturtunately... umm its kinda like gelatin though, same stuff they use in babies diapers I think... I dunno really but I remember seeing it in a garden before, its this jelly stuff.
Anyways, use some of that stuff mixed in your soil, another good thing would be to dig a really big hole for the plant, mix in soil with good drainage, and good water rentention. I was gunna say create a bowl so that any rainwater will collect towards the plant, but seeing as it wont rain much in the okanogan that wont really do much anyways. Cover your soil with some mulch to hold the water in, and expect to have to water quite frequently. Your plant is gunna be getting some good hot sun so its gunna need lots of water good luck
