I live 5 miles NE of the sensor. On sunny days I’m about 4-5 degrees cooler, on nights I’m as much as 10 degrees warmer. I live on First Watchung Mountain about 300 ft higher than SMQ and Duke Farms and the climate is considerably different not being in the bottom of the Raritan Valley closer to the river.
I personally think Duke Farms and SMQ are accurate. For example, on July 16 (the hottest day of this month), the maximum at Duke was 100, SMQ was 98 and my station on the hill with a lot of trees was 94.
From what I’ve seen small changes in vegetation and elevation make a big difference.
For example, in the Adirondacks in upstate New York, KSLK and Gabriels (Mesonet) are within 100 ft elevation and 2 miles from each other, but the temperature can vary considerably. Both high quality stations with good siting.