The time step will influence ...

The time step will influence how the input data in used. Ideally the simulation time step will be the same as the precipitation data interval. Using longer simulation time steps than the precipitation will lump multiple precipitation measurements into one calculation, which effectively averages out the precipitation rate over each simulation time step and reduces precision. Using smaller simulation time steps than the precipitation data interval will divide the precipitation data over multiple time steps and would show a higher degree of precision in the results than could confidently be modelled based on the input data.