A natural, necessary resting time for hosta. Temperatures must drop low enough to cool the ground and stay cold. For many of us there are variations to winter temperatures. Every day does not have to be extremely cold but you do need temperatures low enough to keep the ground cool and hosta dormant. Warm days followed by cold nights will keep the ground cool.
Exceptions can be southern exposures in early spring.
The ground may warm here too early for hosta if your winters are short with marginal temperatures. The reverse example is northern exposures. That's what we call them. Locations in the South and South West with very warm winters. They're charted as zone 9 but in reality are warm micro climates.