London's Tube stations are incredibly hot mid summer and so are New York's subway stations. Melbourne's and Sydney's stations are too, if the weather is hot. You hopefully don't want to wait too long in such conditions. Transport for London (TfL) is spending large amounts of money to cool some Tube stations, lines and the trains themselves by various means.
The difference when a New York or Australian train pulls up and the doors open, is wave of cool air falls over you. Generally in London you do not have that experience and it can be hotter in the train than on the platform. However, there are quite a number of new trains do have airconditioning.
But for the very tight tunnels of the deeper tube lines, little can be done at this point.
Remember the Boris Bus from my post back here? Boris is just nickname for the modern Routemaster bus, after former London Mayor Boris Johnston. I think they were built in 2012 and they were certainly on the streets of London when we were last there in 2014. Unbelievably, they were not built with airconditioning. Not only that, they don't have opening windows. There is an air cooling system, but really, can that be possibly effective? It seems not with internal bus temperatures reaching the mid to high thirties on hot days. Ridiculous and absurd.
Does London only have one or two hot days each year? No, 1976 saw 16 consecutive days with temperatures over 30 degrees. Five days saw over 35 degrees. That is close to 100 in the old money. Heat can be very unpleasant to deal with but in southern Australia, a succession of temperatures over 35 would be very unusual. Never mind, everywhere we go, like in New York is properly cooled. High temperatures are not normal for London, but they do happen and they lead to old people dying. That new buses were designed, ordered and bought without airconditioning is a disgrace.
Just thinking aloud, while air can both heat and cool in Australia because it never really drops below zero degrees here, I don't think aircon can effectively heat below zero, so the present heating would probably be needed as well. I assume Boris Buses do have some heating, at least.