CLI Forward Fundamentals, page-179

It would seem that a light frost would benefit hemp harvest but heavy frosts could be determental:

"Fall Frost
Early fall frost that frequently affects many areas of the Canadian Prairies could be beneficial for hemp growers. Below zero temperatures act as natural desiccant, facilitating maturation of the crop and permitting earlier and more effective combining. It is particularly advantageous in the case of late maturing, fibre type varieties where leaves and bracts can remain green and the seeds are mature. A killing frost causes leaf drop and desiccation of the seed head, leaving bare stems and reduced biomass volume to be combined." ( source: hemptrade.ca )