Based on the records from 1951 to 1980 for 130 weather stations over China the characteristic features of areal and temporal distribution of standard deviation of monthly mean air tempeeatures are investigated. In addition, the relation between the variation of this standard deviation and the position of the climatic frontal zone is also analysed. It is found that the area of high values of the standard deviation coincides with the position of the climatic frontal zone and they both move southward in the winter months and northward in summer.