Where will the faint thunder and rain come from?

From Ye Wan Ji (Volume 11) The Short Song of Thor, Makoto Shinkai's film The Court of Words and Leaves quoted these two sentences.

There are always two words: weak thunder and cloudy sky, but I hope the storm will come and I can leave you here. There was a faint thunder and a cloudy sky. Even if it doesn't rain, I will stay here.

This sentence means talking about love. Everyone wants the other party to stay, and the other party has the same intention. I hope that lightning and thunder will come and the storm will come, so that we can be together.