I cannot STAND cold, and 12 C is practically freezing down here in Sydney. All but torturous, the cold, and it's not even winter yet!
I would really love to live at a place where the highest temperature never goes above 18C, so that 12C sounds like a heaven!
12C is not considered warm but it's a nice temperature for taking a walk if there is not much wind, not too cold and not too hot.