Such cooling may occur as air pressure reduces with altitude, as noted in the article on lifted condensation level.

The altitude at which this begins to happen is called the lifted condensation level, which roughly determines the height of the cloud base.

Espy's formula for Lifted condensation level (cloud base)

As a parcel of air lifted in a thermal rises, it also cools, and water vapour will eventually condense to form a cloud if the parcel rises above the lifted condensation level.

In such case, cloud base begins at the convective condensation level (CCL), whilst with mechanical lifting, condensation begins at the lifted condensation level (LCL).

The lifted condensation level or lifting condensation level (LCL) is formally defined as the height at which the relative humidity (RH) of an air parcel will reach 100% when it is cooled by dry adiabatic lifting.

The usual way of finding the LFC is to lift a parcel from a lower level along the dry adiabatic lapse rate until it crosses the mixing ratio line of the parcel: this is the lifted condensation level (LCL).