A spray cooling system for extreme environments for providing a desired enclosed environment for electronic devices regardless of external environmental conditions. The spray cooling system for extreme environments includes an enclosure that isolates the electronic components from the external environment, a spray unit within the enclosure for thermally managing one or more electronic devices, a pump unit fluidly connected to the spray unit, a heat exchanger unit fluidly connected to the pump, and a control valve fluidly connected between the heat exchanger unit and the pump. An independent chamber preferably houses a heater unit, a first power supply and a control unit, whereby the heater unit initially heats the coolant within the independent chamber to a minimum operating temperature prior to operation of the electronic components.