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We also bought our basilWe also bought our basil plants at Trader Joe's. I brought them in for the winter and just kept them in my living room by the window (it's even a window that faces west so it only gets sun after, maybe 1 or 2 pm.) The plants did fine and I just put them back outside. Our nighttime lows aren't as low as yours though, I think it's only gotten down to 38. Maybe just sit them out in the day and bring them in at night. Good luck!