I think it would most closely be something along the lines of "read the mood" in English, because it's talking about something that isn't spoken but rather felt in the way someone is talking to you. To 'read the air' could be to enter a room and immediately feel as mood difference from the people in the room, or to understand what a person is telling you at a higher level than just what words they are saying, but rather understanding what the specific person is either implying or what emotions are being felt at the time. the 'air' is seemingly not tangible just like the 'mood' of someone or multiple people, yet some people can feel when somethings off, while more clueless people can't 'read' it at all.
