The steady laminar boundary layer flow of water along a vertical stationary uniform flux plate is studied. The working fluid is water whose density-temperature relationship is nonlinear at low temperatures and viscosity and thermal conductivity are functions of temperature. The results are obtained with the numerical solution of the boundary layer equations and cover the temperature range between 40 and 0 degreesC taking into account the temperature dependence of mu, k and rho. Both upward and downward flow is considered. The variation of mu, k and rho with temperature has a strong influence on the results.