The effects of transient temperatures and pressures on soil water hysteresis were studied under controlled laboratory conditions. Variations in ambient pressure and temperature caused small changes in soil water hysteresis. These changes suggest that at least two mechanisms may be present, neither of which is easily rationalized by the classical hourglass-shaped pore liquid jump model.The variation between duplicate samples of a silty clay, a silt loam, and a loamy sand suggested that normal temperature and pressure changes in the field will not cause changes in soil water hysteresis that are larger than those due to natural soil heterogeneity. Consequently, soil water hysteresis curves measured in the laboratory on representative samples may be used in computer models of field situations.