My assumption is that Newark, the city, is just far enough inland not usually affected by cooling from the nearby Atlantic Ocean/bays/rivers. As Forky pointed out, Newark, the city, can be hotter than the airport (EWR the official monitoring station). Even so, EWR seldom is seen to receive a cooling effect. JFK and LGA are right on the water. So, to the best of my knowledge, EWR temperatures are representative of that area. While the monitoring station is above a "grassy" area, we know Newark Airport to be one big paved over parking lot. The nearby Jersey suburbs are normally close to the airports temperatures, but maybe a degree or two cooler. Teterboro airport a few miles to the north, is normally a degree or two cooler than EWR, but Linden Airport is normally within 1 degree of EWR. So, it doesn't surprise me that Newark Airport is the hotspot of the 20 mile radius (or so) around NYC. I believe there are some areas of southern Jersey, Toms River, Berkeley Township and parts of the Jersey Pine Barrens, that can be even hotter, but they are not part of this region's discussion.