The problem of analyzing the impact of anthropogenic carbon dioxide on the environment necessitates the study of the soil carbon dynamics. Thermal parameters (heat capacity, thermal conductivity, and thermal diffusivity) play an essential role in the processes of CO2 transfer and production. Considering that these processes depend on the soil texture and other various factors, mathematical description of the thermal regime of soils in a specific area is a relevant task. There are many ways to estimate the thermal diffusivity coefficient, none of which is universal. In this paper, the least squares method is used to estimate the temperature wave attenuation coefficient (thermal diffusivity) for sandy forest soils of Eastern Fennoscandia, under the assumption that the medium is uniform. Also, a method for estimating the amplitude of daily temperature wave fluctuations is proposed and practical recommendations for the measurements are given.