So I did some research. Utah State has a great website with historical weather data. For the US, you can narrow it down to a single observation station, so I used Central Park, where the records go back to 1876. It turns out that the average temperature for November 14th in the 134 years since then is 48 degrees, which is in line with my guess.
But it's been significantly warmer than that in my lifetime. In fact, the day I was born, in 1951, the high was 67! (The record high is 72 in 1993 and the record low is 20 in 1905.) Not only that, in the decade from 1951 through 1960 it was actually 60 or warmer on every 11/14 but one, the exception being 1953, when it was 44 degrees. The average high for all the birthdays in the first decade of my life was a surprising 61.5. (If it hadn't been for the one cold day pulling the average down, it would have been over 63!)
For the succeeding decades, the average 11/14 high temperatures were as follows:
So yes, maybe there's a slight upward trend there, but the lifetime average for my birthday turns out to be 55.6. So where did I get the impression that it's usually so much chillier?
Weird; and the high yesterday was 61.
Well, at least now I've set myself, and the record, straight.
Happy birthday to all my fellow Novemberites. May you have lovely weather for it.