In winter, the air above us doesn't move randomly. It lingers for several days in the same pattern, like a person who stays in one room before moving to another. There are four such rooms, each with its own weather: one over Europe is warm and humid, another over Siberia is frosty and clear.

Scientists gathered data on air flows over many winters and applied a mathematical technique that finds these rooms and shows how often air moves from one to another. It turns out that transitions are not random: air typically moves in a cycle, from room one to room two, then back, then to room four and three. In each room, it lingers for about a week, but sometimes, especially in room three, it can stay for a whole month.

Previously, it was hard to tell which recurring air patterns were real and which were just random coincidences. Now we have a way to find the real rooms and predict transitions. It's like learning to read the blueprint of the maze that winter air wanders through.