The load capacity of the operating cable is mainly affected by the thermal parameters of surrounding soil， such as thermal resistance coefficient， specific heat capacity， and ambient temperature. However， at present， little research has been done on the thermal characteristics of the soil around cables， and the influence of rainfall is seldom considered. Guangzhou Wushan area is taken as a typical representative， its soil temperature， thermal resistance coefficient and specific heat capacity are measured， and the effects of rainfall on soil thermal parameters are studied. Based on the dynamic load capacity forecasting model of transmission cable and the correlational studies of soil thermal parameters， the emergency load capacity of cables in different initial conditions is calculated. Finally， the influence of rainfall and its duration on the emergency load capacity of cables is analyzed. The research results can provide a reference to the studies of short-term emergency load capacity of cable and cable heating during short-circuit fault.