it's just... mild. Like, you walk outside, and it doesn't feel that cold. It's not like it's been 70+ (although we've had 6 days of 60s this month in DC). I think you are seeing the same thing in the urban areas all up and down I-95. There just isn't much cold air around, so at night, the UHI basically dominates. Sure, your typical areas will get their radiational cooling. But we're talking 20s at night - not exactly frigid.
I think the most disconcerting thing is that literally after a frontal passage, it STILL struggles to get below freezing. WTF?