It is worth noting for my top 3 warmest winters, the frost depth stayed under 6″.
Below is a table that shows the top 10 warmest winters since 1999, and the maximum frost depth. Note that except for 2016 and 2020, the frost depth was no greater than 7.5″.
Top 10 Warmest Grandville Winters since 1999
So, why was the frost depth so deep in 2016, even through it was relatively warm winter? It’s a function how persistent the cold temperatures were, in combination with the snow depth.
In 2016, through it was an overall warm winter, when the frost depth got to 11.5 inches in mid February the snow depth stayed under 3″. Meanwhile the 7 day running mean temperature fell to 16.5 degrees. This year our lowest 7 day running mean temperature was 17.8 degrees, not really all that much warmer than in 2016, however this year the snow depth during that time was between 12 and 16 inches. The point being, to get a deep frost depth you need less than 5″ of snow depth and a 7 day running mean temperature below 20 degrees.
themarinocast 