insulate and ventilate
there is still time to try to save them.
2 inches foam insulation board at least till the temps rise.
with a opening the same as your bottom entrance.
ventilate the top at the highest point about a 3/8'" hole clear through the top board.
wait till next year, maybe they'll survive. maybe they won't.
if all one has done for them is wrap with tar paper, that's no insulation what so ever.
would you live in a home with only tarpaper and wood?
and yes i am from south Florida, couldn't wouldn't stand the cold even in Georgia