A systematic method of measurement of the liquid breakthrough of macroporous membranes at high temperatures is introduced. The method is based on the construction of the initial part of the "flooding curve", performed by experiments carried out in a proper apparatus described in detail. Protocols have been defined in order to get a measure of the volume flux across the flooded pores, at temperatures higher than the normal boiling point of the non-wetting liquid. To the best of our knowledge, the basis of the Liquid Entry Pressure measurement at high temperatures is presented for the first time and experimental results are documented in the temperature range from 20 degrees to 140 degrees C. The new concept of Liquid Entry Temperature is also introduced. A new theoretical-based criterion of data elaboration has been developed. The concept of "normalized volume flux" has been introduced to compare results at different temperatures and to allow an improved definition of the minimum Liquid Entry Pressure. An overall characterization of the process applicability of hydrophobic membranes has been made possible. Prototype macroporous hydrophobized membranes supported on multilayer ceramic (titania) mono-channels were tested. The protocol of measurement has been validated by a commercial PTFE membrane also.