Yes, the TheraFrost (including the chiller) can safely remain outside even during winter and with freezing temperatures. However, keeping the chiller running is important to prevent the water from freezing in the pipes. The chiller also features a built-in frost guard that prevents the water from freezing. If you decide to unplug the chiller, make sure to properly winterize the plunge by draining the tub and the chiller, and by removing the filter housing.