How do hydrogen bonds form between water molecules?

Hydrogen bonds form between water molecules due to the polar nature of the O–H bond within each molecule. Because oxygen is more electronegative than hydrogen, it attracts electrons more strongly, resulting in a partial negative charge ($\delta -$) on the oxygen atom and a partial positive charge ($\delta +$) on the hydrogen atoms.1

These charges create an electrostatic attraction between the hydrogen atom of one water molecule and the nonbonding electron pairs of the oxygen atom on an adjacent water molecule. This interaction is known as a hydrogen bond. While these bonds are weaker than covalent or ionic bonds, they are strong enough to significantly influence the physical properties of water, such as its high boiling point, viscosity, and surface tension. In liquid water, these bonds allow molecules to form and re-form aggregates continually, while in ice, they create an open structure that makes solid water less dense than its liquid form.12345