When you dream thunder means: A thunderous dream suggests that there is a potential pressure overload, and it could explode. Lightning strikes creates a thunderous sound, which can be symbolic of a rapid release of tension that could prove to be destructive. It could indicate fear, insight or realisation in your life. As these suppressed feelings can often explode, they are known to cause powerful bursts. You might also feel the release of situations beyond your control.
(in Dream Dictionary)