Because of the significant impact of meteorological factors on the load， the accuracy of load forecasting should beenhanced by taking these factors into rational consideration. The accumulative effect is an important phenomenon ofsummertime meteorological factors influencing the load. It refers to the fact that the temperatures of the few days before theday to be forecast have fairly obvious influence on the load of the to-be-forecast day， the effect being especially appreciable insustained summer heat. An analysis of large amounts of meteorological data shows that， under different conditions， theintensities of the accumulative effect are different， as are their influence on the load. For this reason， a new method is proposedto have the intensity of accumulated effect reflected by the discrete accumulated coefficient and temperature modifying formula.Various influencing factors have been considered， such as the temperature of the to-be-forecast days， the number of sustaininghigh-temperature days， etc. It is proved by a case study that the method proposed can fairly accurately reflect the influence ofthe temperature accumulative effect on the load.