Jack, indeed Black Sea make our climate much milder than in most part of Ukraine, and as in other part of Crimea it create micro-climate which is specific to our only region. Unfortunately we live on flatland, and don't have any mountains, forests or even hills nearby. So when we got Northern winds our air temperature may drop significantly for short time but later return under influence of Black Sea and Sea of Azov.
It's shame but I've never heard of Koppens classification, is there any resource online to see these maps freely?
Also Sochi have unique placement which seems to grant it such almost tropical climate, in our country similar position have Yalta which have very mild winter.
Regarding my city it have hot summers upto 40 Celsius in shade sometimes and most winters are mild and I agree with average temperatures listed here: Kerch, Ukraine - Sunrise, sunset, dawn and dusk times for the whole year - Gaisma
(you can check this link and compare to your own climate to see if it's colder or not).
But sometimes we get -10 C for week or more and year ago we got one of the coldest winter for 50 years I think, it was -29 Celsius and also for almost week(surprisingly we had a lot of snow so nothing was damaged in garden, only some cactuses died on my balcony).
But the worst thing is our winter are most of time snowless:P