Official Explanation

B, D

“Despite” is a classic detour road sign indicating that the sentence will change direction. You’re told that the weather is bad, which normally puts people in a “foul” mood, so the blank must have a meaning opposite of that because of the detour road sign. “Happy” works well. Based on that prediction, you can reject (A) disconcerted, as that means “upset,” and (E) histrionic, as that means “melodramatic.” Choice (C) garrulous means “chatty,” so that does work in this context, but no other answer choice creates a similar sentence. Choice (F) sententious means “given to excessive moralizing,” so that doesn’t work in this context.
Choice (B) jocund, meaning “jolly,” works and creates a sentence similar to the one created by (D) genial (“warm and friendly”). They’re your answers.