Speaking as a Canadian, there's a reason there isn't a homelessness problem up here like California's, and it isn't our healthcare or social plans. If you haven't ever seen a frozen corpse, you don't work within a city, that's for sure. All the major cities have departments who need to pick up the frozen dead on the regular. And it isn't like those homeless are transplants from Cali, they're also Canadians, and know how to deal with the cold. The knowledge doesn't change their life expectancy from "next February", though.

Now, these people DO have homes, and given A/C is a thing, I imagine they're insulated homes which would help, but if they aren't, then yeah, gonna have a few not waking up if they're dumb about it. But I think blackouts will not kill from cold so much as from key electronics: People who have at-home medical equipment, in example.