Well i have seen it done late into fall and early winter. here are some tips. Dig a hole to place buckets into ground to keep root warmer . This will aslo keep the plant lower to the ground. then you can use some 2x3 or 2x4 lumber to build a simple frame.Then staple clear plastic to it. This will give you a small greenhouse to place over it on the cooler day and at night.Depending how close it is to electric source you can always run a power cord for a small heater if it get cold towards the end of flowering.As long as the sun is shining directly on it. The plastic will hold the heat in quite well.Also the person i seen do this made mini greenhouse about 6 inches taller then plant.he then lsd or tied plant down .It worked quite well he harvested plants in early december, people just scratched there head when he told them they were from outside. As long as temps are ok and they get 8-10 hours of direct sun you will be more then fine.