The paper presents detailed comparisons for numerical simulations of fire development along the facade, with particular emphasis on the so-called “leap frog effect”, for different variations of window opening sizes and storey heights. A total of 9 models were subjected to numerical analysis. The problem occurred in most of the analyzed models – i.e., the fire penetrated through the facade to the higher storey. It should be noted that the adopted hearth was identified by standard parameters, and materials on the facade were non-combustible – as a single-layer wall. In the case of real fires, the parameters of the release rate can also vary greatly, but the values are usually higher. It has been shown that the most dangerous situation is with small size windows, where the discharge of warm gases and flames, causes a fairly easy fire jump between floors. The leap frog effect can be limited by increasing windows and storey height – this changes the shape of the flames escaping from the interior of the building and limits the possibility of fire entering the storeys above. In addition, increasing the size of windows results in a reduction of fire power per unit window dimension [KW/m2] at constant fire power (fuel-controlled fire), which is also of key importance for the fire to penetrate with the leap frog effect.