Tumbleweed is a name for a teacher who constantly travels around the room when the class is busy at work. When the "wind is blowing", the teacher moves around the room at rapid speed, traveling from desk to desk (or table) just to make a good conversation, or to check up on how your doing, then travel to another student right after the teacher is done talking. When the "wind isnt blowing", that means that the tumbleweed (teacher) sits at the desk or computer in silence in their chair while the class does independent work.
Student 1: Oh god, here comes tumleweed. I guess the wind is blowing because he is running over here. He was just across the room!
Student 2: Oh tumbleweed. What a silly man. Always moving around.