Best time is in October (last too weeks). A this time the Bears gather in Churchill waiting on the bay to freeze over. I went in July and there were a couple of bears in town.

I agree – keep in mind though, that bears are never a sure thing, thought we saw a lot in late fall (plus the Northern Lights). It’s worth the effort to be part of a tour group that goes out onto the tundra, and some tours even have facilities to let you spend the niht on the tundra – that will definitely increase your odds. Have fun!