Each fall there is a period of frost, but days with enough heat so plants can survive and remain alive. Ken erects what he calls hoopettes over crops that will take some cold weather. The season can continue for quite some time. It all depends on the weather!
If the snow falls and covers the soil like a blanket, and the frost does not creep in and freeze the soil in the hoopettes, the plants can take below freezing temperatures. Some years, like last season, it stays warm and the season continued up to Christmas!