That there's a lot o' territory I've considered going to -40 in the summer here in sunny Florida. It just doesn't get driven in serious heat and low speeds enough.... Ultimately, any full synthetic in either 5W-30 or 5W-40 that is fully API certified for today's criteria will work fine under conditions warmer than the arctic circle and cooler than the equator.
To OP: There are probably a hundred threads on oil choices and just about as many opinions, so I'll not add my personal preference. I hate to say it, but "search and ye shall find."
Ultimately, any full synthetic in either 5W-30 or 5W-40 that is fully API certified for today's criteria will work fine under conditions warmer than the arctic circle and cooler than the equator.