"It will rain tomorrow" is true .. or will it be ..?

1.will and going to can both be used in weather, so both can be used.

2. The second question is B because although the main clause appears in the predicate, it is not a past tense, but a tactful way of asking questions. Therefore, the clause still uses the general future tense to represent the future weather, so a's could is wrong.

In this topic, it is not a sentence pattern, but a tense.