I lived in Piscataway for 36 years. I always noticed that area was a bit warmer than some other surrounding spots. Maybe it had something to do with the Watchung "Mountains" to the NW of town. I moved about 10 miles west and there is a few degree difference here most days.
7 for the low. Must be close to double digits with times below 10 this season if not already there. I'll have to check Somerville's stats.
Edit: looks like 10x in Somerville, not bad. 4 total last winter.