Storms represent emotion and thoughts. If someone dreams about a storm occurring, their mind and heart may be at conflict with each other.
Storms can indicate a miscommunication, difficultly expressing one's thoughts or a misunderstanding. This includes real-life issues like holding a grudge against someone or not being able to make a decision that has an important impact on a person's life. A rainstorm in particular may represent emotional stirrings or cleansing. Someone may have negative thoughts that require washing away so that they can restore the health of their psyche and return to their regular path in life.