Do you think "outside" is redundant? My child said "We won't imagine 'It's raining inside'".
Yes, it's redundant. That doesn't mean you won't hear it. People say "What's the weather like outside?" etc quite frequently and they will also include "outside" in the answer, but it adds nothing. Your child is right - it's very unlikely to be raining inside. We generally don't have weather inside.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.