Yeah I think it was 2015 - in NYC, it was the warmest Dec on record. It was warmer than Nov that year and the avg temp in December would've been like a top 10 November. Just insane.
i think that's the thing that's really been noteworthy over the past, I dunno, several years. We haven't had insane heat (generally) - it's just warm. Basically wire-to-wire.