What mood or tone is created by the witch's predictions?

The weather is dark and stormy whenever the witches appear. This sets the mood for danger and mystery. The tone of the witches is darkly playful on the surface. They speak in near riddles. The audience, however, is well aware that there is dark magic suggested whenever the deal with Macbeth. The witches also speak in equivocation, which is a reoccurring motif in the play.