User blog comment:Xilinoc/Ch. 542 - THE BLADE IS ME/@comment-4207271-20130620040906/@comment-11051098-20130623125916

Well, it could turn out that Zangetsu really is a water-type Zanpakutô. As people have said, Kaien Shiba had a water-type, and being related to him, Ichigo could have it too.

The rain could be a symbol of that.