Jet impingement cooling apparatuses having non-uniformly sized jet orifices for producing an array of impingement jets that impinge a target surface are disclosed. In one embodiment, a cooling apparatus includes at least one fluid inlet channel, at least one fluid outlet channel, a target surface, and a jet orifice surface that is offset from the target surface. The jet orifice surface includes an array of jet orifices fluidly coupled to the at least one fluid inlet channel, wherein each individual jet orifice of the array of jet orifices has an area corresponding to a distance of the individual jet orifice to the at least one fluid outlet channel such that individual jet orifices closer to the at least one fluid outlet have an area that is smaller than individual jet orifices further from the at least one fluid outlet. Power electronics modules are also disclosed.