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The loss factor of supercooled water at the frequencies 11 . . . 180 GHz has been measured. A measuring technique has been proposed, in which wetted nanoporous silicate materials, silica gels, with the mean diameter of the pores being 6 − 9 nm, were used to obtain deeply supercooled water. Results have been obtained for the loss factor of supercooled water, close to volume water for its properties, when cooled down to −45 • C. To ascertain the mechanism of pore water losses, measurements have been made in the range of temperatures 0 . . . − 90 • C. The results obtained have demonstrated the existence of significant excessive losses at the temperatures below −30 • C, compared to the results of computations based on the known models. To allow mathematical description of the increment loss factor, a new addend has been introduced as a sum of two Gaussian functions in the formula described in [T. Meissner, F. J. Wentz, IEEE Trans. Geosci. Remote Sens. 2004. vol. 42, p. 1836. One of these functions has the extremum near −45 • C, and the second one has the extremum in the range of −60 . . . − 70 • C. Additional attenuation at −45 • C is supposed to be connected with the second critical point of water. Attenuation with the center in the range of temperatures −60 . . . − 70 • C is determined by the emergence of conductive films at the boundary between the hard matrix and ferroelectric ice 0. This modification is a transitional form to ice Ih or ice Ic and is formed at the temperature below −23 • C.