what if 是
介词短语,常用来表示未来如果发生某事(通常是不好的),该如何处理,常译作:如果……怎办?
Tony: Hey, John, this Saturday, can we go together for a picnic with our girlfriends?
John: Sounds great, what if it rains cats and dogs this Saturday. Don't worry, let me check the weather forecast in a while.