One complete year of continuous observations of vertical radiation of the atmosphere in two points of millimeter wave band (94 and 38 GHz) was conducted. The total vertical absorption, liquid and vapor water content of atmosphere, and average (effective) temperature of clouds are restored on the basis of these two-frequency radiometric data. Numerous cases of abnormal differences between experimental and theoretical values of cloud absorption at the two frequencies were observed. An analysis of the collection of direct and indirect features that accompany the abnormal events is carried out. It is shown that the main sources of observed abnormal differences between theoretical and experimental data are snow and ice particles in clouds and, probably, water droplets of large size. The possibility of using two-frequency radiometric data not only for retrieving of liquid and vapor water content of atmosphere but also for determining the effective temperature of clouds and for assessing hydrometeor microstructure is noted. For this purpose, polarization measurements are very useful.