A method for operating a fuel cell system comprising a fuel cell assembly of a plurality of fuel cells configured to generate electrical power from a fuel flow and an oxidant flow to the plurality of fuel cells, the fuel cell assembly arranged in combination with a coolant storage module configured to supply the fuel cell assembly with a flow of coolant, the method performed when the temperature of the coolant in the coolant storage module is below a coolant temperature threshold and comprises; a first phase performed prior to activation of a coolant pump configured to deliver coolant from the coolant storage module to the fuel cell assembly and a second phase performed after activation of the coolant pump.