The storm that occurs at the beginning of Act Two of Othello is one that causes those waiting on shore to be unable to see what lies ahead on the water. The governor, Montano, wonders, "What from the cape can you discern at sea?" A gentleman replies, "Nothing at all. It is a high-wrought flood."
This situation is symbolic of what is later to come in the play. The characters will become so immersed in their own emotions and personal turmoil (the "storm" of their lives) that they will be unable to see the forces at work behind that storm (namely Iago's manipulative words and actions) and the truth through the "flood." This inability to see clearly in the midst of chaos is what ultimately leads Othello to murder his own wife via strangulation and to commit suicide in the final act of the play .
The storm serves as an element of foreshadowing for the main characters involved in this play, including Othello, Cassio, Roderigo, Emilia, and Desdemona. The storm, as foreshadowing, leads the reader to believe that perhaps a storm of other sorts is coming (mainly Iago's plot to ruin Othello through his jealousy). Also, the storm is symbolic of the turmoil to come in the play. The storm is also symbolic of Othello's temper, which is short and fierce.