The Bible says the rainbow was God's promise not to wipe out all life with a deluge ever again.
He will indeed use fire the next time. Not a favorite topic for me, but it does say that.

Your eyeballs will melt and run down your faces.
I'd rather drown to be honest with you.
The sun could go nova, or fire called down from Heaven like the prophet Elijah incinerated some pagans.

Elijah replied to the captain, "If I am indeed a prophet, may fire come down from the sky and consume you and your fifty soldiers!" Fire then came down from the sky and consumed him and his fifty soldiers.