Actually, not that high yield, judging by the simulator Pastor Brooks linked.
Looks like about a 50-60 KT warhead going off in Chinatown, and another of similar size going off on about the border between Brooklyn and Queens. Really, not all that high yield... by the B61 standard of dial-up yields, these would only be considered moderately-large Tactical warheads, not even Strategic warheads at all.
But that's sorta bad news, as the devastation even two of these "little nukes" would wreak on the city is obvious from the depiction; and such smaller, battlefield-class warheads (of which the Soviets had tens of thousands in the 1970s-80s -- though many may have since substantially decayed in yield, or even become inert) would probably be the ones more likely to fall into the hands of Islamist terror groups (though still very unlikely at this time, I hope).
Sorry, “Books” not “Brooks”. Mea Culpa.