The article is devoted to the issues of taking into account the influence of temperature when measuring salinity and electrical conductivity of soil. It is determined that well-known studies on the implementation of ground-based validation of space data on soil salinity inevitably contain uncertainty due to different temperature values of the actually probed soil and the temperature of the water-soil solution used in laboratory validation studies. A well-known technique for taking into account the influence of temperature on validation results in the form of using a polynomial temperature coefficient and a reference value of soil conductivity at a temperature of 25 ℃ has a specific uncertainty due to the measurement error of conductivity at a fixed temperature of 25 ℃. A criterion different from the known criterion is proposed and the task of calculating the optimal type of the temperature correction function is formulated, taking into account the introduced criterion. Thus, it is possible to eliminate the uncertainty caused by the difference between the unknown temperature of the probed soil and the temperature dependence of the electrical conductivity of the soil during validation measurements of the water-soil solution.