Ok, so, let's try to summerize in one post the different locations outside the Known World where survivors might be found:
North America:
—Scattered survivors community accross Canada and Alaska, with the most prominent in Newfoundland, Nova Scotia and Prince Edward Island.
—The Appalachians.
—The Dakota badlands and indian reservations of the upper Midwest.
—The Rockies.
—Greenland (I'm putting Greenland here for convenience, this is not a political statetement don't be mad plzkthx)
South America:
—The Andes.
—The Tierra del Fuego peninsula.
Africa
—The only place that gets somewhat cold in the winter and offer natural protection are the Cape Fold mountains in South Africa and the Lesotho mountain range. Other mountain ranges in Africa are right into the tropical zone and see no winter at all.
Europe
—The Alps.
—The Carpathians.
Asia
—The Urals
—The Altai
—Siberia in general (scattered groups)
—The Caucasus mountains, eastern Anatolian plateau and Zagros Mountains (in spite of their low lattitude, pretty close to subtropics, these regions turn out to have much colder climate than surrounding areas of similar lattitude).
—The Tian Sha mountains (mostly over Kyrgyzstan).
—The Tibetan plateau and the Himalaya.
—The mountains of western Mongolia.
—Japan (only Hokaido and northern Honshu, if they failed to contain the flows of east asian refugees).
Oceania
—Possibly Tasmania and southern New Zealand.
—Most micronesian and polynesian islands.
Antarctica
—The Amundsen–Scott South Pole Station, if they managed to somehow create a self-sustainable organisation.
—The McMurdo Station.
—King George Island.
Agree/disagree?
edit: added the Rocky mountains.
edit: added Micronesia and Polynesia.
edit: added stuff