To obtain a fundamental understanding of the transport regimes governing the electrochemicalbehavior and ageing of the polymer electrolyte membrane fuel cell, the measurement of themembrane in- and through-plane water distribution is essential. In this paper, operando -Raman spectroscopy is used to probe the water content of the Nafion® membrane in a modelfuel cell working at constant stoichiometry and relative humidity. Water concentration profilescrossing the membrane thickness are obtained with m resolution at different locations of theactive surface: at the middle and close to the inlets/outlets of the reactant gases, at the feed gaschannel and under-lands areas. The influence of the operating temperature and of the currentdensity delivered by the cell are investigated. Of particular interest for perspective fuel cells,the membrane inner water partition appears highly heterogeneous when operating at ambientconditions, and dependent on the delivered current. The increase of temperature decreases themembrane water content at all the probed positions and induces a less uneven water distribution.The membrane hydration appears to be a key parameter for understanding the waterredistribution between cathode and anode with the change of the cell operating conditions.