That's global warming for you; the city's in a dip between the hills, and i remember some cold weather when I was a kid! Every winter the snowploughs would be out at some point, and there would be piles of grey snow along the roadsides for weeks afterwards, slowly melting. Sometimes, in still winter weather, a pool of cold air would form, and the smoke from the chimneys would sink back down into it and sit there in a sort of hazy layer round the houses.
