Maximum ice coverage in the Sea of Azov: February.
First ice in December, in some exceptionally cold winters (once in 5-10 years in the XX century) in November.
Historical monthly average temperatures in Taganrog(one of the coldest places in winter in the Northern Azov):
http://www.pogodaiklimat.ru/history/34720.htm
This is from Soviet archives so no data during German occupation.
German data from that area and period are there:
Julius Büdel. Das Eis im Kaspisee // Annalen der Hydrographie und Maritimen Meteorologie 1943
Maps of the ice coverage can be found in this article:
https://ice-snow.igras.ru/jour/article/view/488/280
The 1941/1942 winter was not very cold in the Azov region.