The ground below Lambeau Field has been heated since 1967, when Coach Vince Lombardi oversaw the installation of electric coils that zig-zagged under the turf like wires in an electric blanket. The aim was to keep the ground soft enough so that cleats could grab hold and players could keep their footing.
For 30 years, those coils kept Lambeau Field soft, with one exception. That came months after installation, when the Packers played host to the Cowboys for the 1967 N.F.L. championship. Temperatures well below zero were too much for the system. The field grew stiff and slick. The game was nicknamed the Ice Bowl. Writers in the aftermath dubbed the playing surface the “frozen tundra.” The term stuck. It remains frozen in time.
The electric coils were replaced in 1997 by a system of pipes filled with a solution including antifreeze. These days, the temperature of the soil is controlled by the field manager
Allen Johnson. With temperatures Sunday expected to be in the 20s, Johnson will probably set the soil temperature to about 40 degrees. That will be enough to offset the subfreezing air temperature and keep the field soft.