A system for detecting humidity level at a cathode of a fuel cell stack including one or more PEMFCs and determining a flooding probability of the stack based on the humidity level, includes a stack including a plurality of PEMFCs, each PEMFC including an exhaust; voltage detector; humidity detector; and controller. The controller may be configured to: receive a voltage as measured at an anode of one or more of the PEMFCs with the voltage detector; determine a humidity level at the exhaust of the one or more of the PEMFCs; and implement one or more actions based on the voltage and the humidity level, the actions including: reduce a load on the PEMFC; increase an air flow at a cathode of the one or more PEMFCs; decrease an inlet humidity at an inlet to the one or more PEMFCs; or increase a temperature of the one or more PEMFCs.