Most often a coat in a dream is connected to something in waking life you wish to hide, keep under wraps. Less often a coat represents your ability to protect yourself from emotional harm.

A raincoat reflects your need to protect yourself sadness or depression.

If the coat is torn or does not fit or you can’t find it then you are likely having a hard time, in waking life, keeping something private OR difficulty sheilding yourself from an emotional downpour.