They're all good. The third one should be, "I think it is going to be raining soon. Be sure to capitalize the pronoun "I," and the first word in every sentence.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Anonymous"I think it is going to be rained soon" - you gotta be kidding ...
I'm not a native speaker, but this sentence surely is ungrammatical and - possibly - nonsensical