Sea mines in the Skagerrak, a means to generate a record January 1940?

 Due to the high variability of water layers and their different origin the Skagerrak is a particularly sensitive water body to sea mine barrages They often explode prematurely. Since April 1940 Skagerrak was a naval battle field and only few months later the region experienced the coldest January on record:

  Lowest temperatures at a number of  stations

in southern  Norway – January 1941

South-West region (Kristiansand – Stavanger), in: °C.

Chapter: 3_11

Book Page: 157

File: 976_Skagerrak_mines

Image: 2010/www.seaclimate.com