Thunder is usually the forewarning of slander against the person seeing the thunder in his/her dreams.
Your friends, your relatives, your enemies, those who are jealous of you, those who pretend to be your friends and be happy about your successes they are all are (together or separately) gossiping and slandering you.
You will soon find out and be deeply disgusted & disappointed.
The meaning of rain in dreams can vary depending on the context of the dream and the personal experiences and associations of the dreamer.