A pool winterizing system including a pool cover-sheet and a housing that is disposed beneath the periphery of the cover-sheet and in communication with the environment exterior to the cover-sheet. The housing defines an inlet duct and an outlet duct, each of which provides an independent air-flow path between the environment exterior to the cover-sheet and an inflation chamber selectively defined between the cover-sheet and the pool. A blower is disposed within the housing in the inlet duct and provides for inflation of the pool cover-sheet. A flap is hingedly attached to the housing above the outlet of the outlet duct and is biased toward a position in which it covers the outlet duct outlet so as to control the pressure to which the pool cover-sheet is inflated. Operation of the blower can be controlled by a light sensitive switch that "observes" the environment exterior the cover-sheet and, in conjunction with a circuit, causes the blower to operate when it is dark and causes the blower not to operate when it is light. The pool winterizing system further includes a heating system that operates when the temperature drops below a predetermined level.