The magnetic properties of arrays of magnetic nanowires, prepared by electrodeposition in nanopores of alumina membranes, were investigated. The hysteresis loops were measured using a magnetic field applied both perpendicularly and parallel to the nanowire axes for temperatures between 4 and 300 K. The results show a preferred direction of magnetization parallel to the nanowire axis at room temperature, but perpendicular to the nanowire axis below a certain crossover temperature. We observe that such crossover temperature increases by increasing the nanowire length. The results are discussed considering strains caused by the different expansion coefficients of the nanowires and the matrix.