Your post is not very clear but if I understand you correctly, the answer is yes, you can use a present tense (in fact it's better) if the thing is still true (ie. if nothing has changed) when you're reporting. Try understanding your example like this:
'He told me that it is going to rain this weekend.'
[He made a prediction and it remains as a prediction, so stay with the present tense because nothing has changed]
'He told me that it was going to rain this weekend.'
[He made a prediction but the prediction has been confirmed (positively or negatively - for example, you can see that it's raining or there's clear evidence that it's definitely not going to rain) and so is no longer a prediction, so change the tense to past to suggest that the prediction is now in the past]
There's no need to 'backshift' the tense when reporting unless there's a reason to do so. Does that make sense?
Student or Learner