For mobile applications, performance of polymer electrolyte membrane fuel cells (PEM-FCs) should be maintained with being exposed to subzero temperatures in winter time. To simulate such a situation, a single cell PEM-FC was operated at 70{degree sign}C, stopped, kept at -10{degree sign}C for 8 h, and heated to 80{degree sign}C for the next operation. The cell was unable to work. The degradation was attributed to freezing of water present inside the MEA, produced during operation, and remained in the PEMFC after the operation. To prevent the performance degradation, water was removed from the PEM-FC by supplying dry N2 to the PEM-FC before the cell temperature fell down to -10{degree sign}C. Several freezing/thawing cycles were operated to study the PEM-FC performance degradation. Effects of water freezing in the PEM-FC on the electrode structure were examined by SEM analysis.