Saying something contrary to what one truly means, as exclaiming, "What a beautiful weather!" during a torrential downpour, is known as verbal irony.

Verbal irony is a form of figurative language where the speaker says something that is the opposite of what they actually mean. It is often used for dramatic or comedic effect, and can convey sarcasm or satire. Verbal irony can be used to highlight contradictions or emphasize the absurdity of a situation.