To me, the rain at the end of the movie, right when the vote was even, symbolized the split jury and the final encounter with the angry man that was about to come. The angry man, on the other hand, had a very hard time standing alone when he was the only one who still would not change his vote. He resorted to racist comments and an argument that could not stand firm. He was not rational, but stubborn in his actions. He communicated his ideas of doubt and helped them through the evidence with rational steps.
All leadership takes place through the communication of ideas to the minds of others.