5. Helsinki (Finland) -33C
Finland's cool capital is surrounded by sea and a vast archipelago, creating a city that blends Nordic urban chic with outstanding natural beauty. The Baltic gets so Baltic that it freezes over during mid-winter, and you can even go ice skating on it. If you prefer snow to ice, pick up a pair of cross country skis and take to the city's Central Park ski trails. And if you're really feeling brave, join the winter swimming teams at Rastila campsite for a very refreshing dip indeed.