This paper considers the question of determining frozen/unfrozen status of 5 cm topsoil layer for seven ground stations in Alaska with latitude from 65° to 70° N by using radar Sentinel 1 C-band data for the period 2016-2017. Determine the status of frozen soil was carried out by two ways: using only radar data with finding the backscatter coefficient threshold, when the temperature in the upper soil layer falls below 0°C, and by using both radar data and ground-based measurements of soil temperature. In the latter case, the correlation between the backscattering coefficient and the soil temperature measured at 5 cm below the soil surface was calculated. Regression models were developed and radar backscatter thresholds for frozen soil were found. Local frozen/unfrozen soil maps were created. The comparison of threshold values obtained by two ways showed their closeness, which tends to decrease with decreasing correlation between radar and ground data. Linear regression between radar backscatter threshold and the area latitude have been received.