Consider the following premises. David is a sailor if and only if it is cloudy. Joseph is a bartender or David is not a sailor. Joseph is not a bartender. Can we infer the following from them? It is not cloudy.
 From the fact that Joseph is a bartender or David is not a sailor we can infer that if David were a sailor, then Joseph is a bartender. From the fact that if David were a sailor, then Joseph is a bartender, and that Joseph is not a bartender we can infer that David is not a sailor. Finally, from the fact that David is a sailor if and only if it is cloudy, and that David is not a sailor we can infer that it is not cloudy. Therefore, the answer is yes.