Abstract An orientational order parameter is specified and determined statistically on the basis of a variational minimization of the local free energy. Central dispersion, dipolar and quadrupolar features of the molecular interaction are incorporated, and the development of orientational order determined numerically across the liquid-vapour transition zone over the temperature range 4–200°C. The development of electrostatic torques at the surface establishes that the water molecule orients preferentially with its protons directed towards the vapour phase. The associated surface potential is determined, as is the surface tension, and will be presented in terms of the dipole-dipole, dipole-quadrupole and quadrupole-quadrupole contributions.