The very high heat of vaporization of water is mainly a result of

The very high heat of vaporization of water is primarily due to the presence of strong hydrogen bonding between its molecules. While water molecules are held together internally by polar covalent bonds, the energy required for phase change (latent heat) must overcome the intermolecular attractions [2]. Hydrogen bonding is a specific, strong type of dipole-dipole interaction that occurs when hydrogen is bound to highly electronegative elements like oxygen. In water, each molecule can form multiple hydrogen bonds, creating a robust network that requires significant thermal energy to break during the transition from liquid to gas. This makes hydrogen bonds significantly stronger than standard van der Waals forces. Consequently, water absorbs a large amount of heat to evaporate, a property essential for regulating Earth's temperature and biological cooling [1].

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > Latent Heat > p. 294
2. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > Explanation > p. 295