The temperature dependence of the geometry of the water molecule in liquid water is calculated as a perturbation of its gas-phase geometry. The perturbation is assumed to depend only on the electrostatic and van der Waals interactions with the surrounding molecules. The geometry shift is thus given by the electric fields, their gradients, and the fluctuation potential obtained as ensemble averages in molecular dynamics simulations and quantum chemical calculations of field and field-gradient derivatives of the geometrical gradient and Hessian of the water molecule. The presented gas-to-liquid shifts (Delta r(OH) approximate to 1 pm and Delta alpha approximate to 2 degrees) are of the same accuracy as both experiment and other theoretical investigations.