改错 What do you do when it's rainning?

What do you usually do when it is raining. raining不能双写n

what did you do when it's rainning?

rainning
改成rain

what did you (doing) when it's rainning?

这句话可以说没有问题！

就是说当下雨的时候，你一半做什么？一般的描述用一半现在时就可以了。