Way back before they started calling it "climate change" I read an article about how a lot of the thermometers used to measure temps are placed areas that give false readings. Some are mounted to the sides of buildings where the building's heat affects the temperature. Some are mounted right above cement parking structures where the reflected heat from the cement affects the temperature. A lot of them, like you said, are not maintained.
I seriously doubt anything has changed because they actually want higher temperature readings, even if they now call it climate change.