In Tokyo, you sweat to death on the subway, then get off with wet underwear into the cold street and yeah, summer trains feel so cold it's like having a high fever when sitting on the train.
JR commuter trains "solve" this problem by having some carriages on longer trains intentionally set to higher temperatures, signposted 弱冷房車 ("weak cooling car").
It's very weird. In my university dorm in the common room, there was always a fight between the local students and the exchange students about the AC temperature.