Usually the rain is the symbol of negative emotions such as sadness and melancholy. Some people who are on depression dream about rain, because it is something that is unpleasant and sad to experience. In some cultures the rain is the symbol of life and growth, therefore you should pay attention to your feelings, how you felt during your dream: happy or sad. The rain for some people is the sign of comfort and stability, so sometimes the rain can have a very good meaning.
Read more about dreaming of Rain in other dream meanings interpretations.