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Towards the high galactic latitude sky, the far-infrared (FIR) intensity istightly correlated to the total hydrogen column density which is made up ofatomic (HI) and molecular hydrogen (H$_{2})$. Above a certain column densitythreshold, atomic hydrogen turns molecular. We analyse gas and dust propertiesof intermediate-velocity clouds (IVCs) in the lower galactic halo to exploretheir transition from the atomic to the molecular phase. Driven byobservations, we investigate the physical processes that transform a purelyatomic IVC into a molecular one. Data from the Effelsberg-Bonn HI-Survey(EBHIS) are correlated to FIR wavebands of the Planck satellite and IRIS.Modified black-body emission spectra are fitted to deduce dust optical depthsand grain temperatures. We remove the contribution of atomic hydrogen to theFIR intensity to estimate molecular hydrogen column densities. Two IVCs showdifferent FIR properties, despite their similarity in HI, such as narrowspectral lines and large column densities. One FIR bright IVC is associatedwith H$_{2}$, confirmed by $^{12}$CO $(1\rightarrow0)$ emission; the other IVCis FIR dim and shows no FIR excess, which indicates the absence of molecularhydrogen. We propose that the FIR dim and bright IVCs probe the transitionbetween the atomic and molecular gas phase. Triggered by dynamical processes,this transition happens during the descent of IVCs onto the galactic disk. Themost natural driver is ram pressure exerted onto the cloud by the increasinghalo density. Because of the enhanced pressure, the formation timescale ofH$_{2}$ is reduced, allowing the formation of large amounts of H$_{2}$ within afew Myr.

A dynamical transition from atomic to molecular intermediate-velocity clouds