Hostas here in the lower Great Lakes Region will not be bothered by a night or two below freezing. I have a forecasted low of 27 degrees for Saturday morning. I am not concerned.
If it was 15-20 degrees, well then I would be.
But that is just me. You can use boxes like Daisy suggested, old comforters, old sheets, frost blankets, anything to protect them. The ground is not currently frozen so if you can block the loss of heat from the soil by a comforter, that might keep them at 35 or slightly higher. That should be more then enough.
Plus they genetically can cope with temperatures around 32 degrees.