<p>This the above sentence incorrect? I read that it is a case where which can refer to vacation or the fact that it is coming.</p>
<p>From my knowledge of relative pronouns, I believe the sentence is correct. This is because relative pronouns always refer back to its preceding antecendent, which in this case is the fact that it is coming.</p>
<p>I'm pretty sure that's correct. In German, I'd say it's definitely correct; I assume the same holds true in English? If it's wrong, I'm not sure how you would rephrase it.</p>
<p>"Vacation is coming" stands alone as the main clause.</p>
<p>"which is nice" is a prepositional phrase modifying "is coming".</p>
<p>While there is some ambiguity in terms of is "vacation" nice? or is "vacation coming" nice, the meaning is so similiar that it won't really pose any problems for anyone.</p>