Thermodynamics of Clouds is Volume 6 of the International Geophysics Series. This volume is an attempt to be a single reference of meteorological works of thermodynamical problems in relation to surface tension and adsorption. Numerous applications of various formulas accompany the text for further understanding of the reader to the concepts featured. The book is divided into 13 chapters where Chapters 1-6 serve as the first part of the book and the second part is from Chapter 7 to Chapter 13. The first part generally discusses and establishes the general formulas of the thermodynamics of surfaces. The method used by the authors is the one by Defay and Prigogine of studying systems in a state of partial equilibrium. The second part of the volume applies the general formulas established in Chapters 1-6 into some meteorological problems such as studies of a droplet or ice crystal suspended in the atmosphere. The text can be used by both graduate and undergraduate students with interest in thermodynamics and climate studies. Professionals such as meteorologists can also use this book as reference in solving some meteorological problems.