Baiu in which not so strong rainfall continues for a long period of time is expressed as negative baiu and is baiu in which, if it rains, a large amount of rainfall occurs in a short time and, if not rains, sunny weather comes is expressed as positive baiu.
あまり強くない雨が長く続くような梅雨を陰性の梅雨、雨が降るときは短期間に大量に降り、降らないときはすっきりと晴れるような梅雨を陽性の梅雨と表現することもある。