The performance of multijunction photovoltaic (PV) devices, such as two-terminal perovskite/silicon cells, is strongly influenced by spectral irradiance distributions, as current matching among sub-cells is highly sensitive to spectral variations. In desert regions, the increasing frequency of dust and sandstorms may significantly alter the spectral distribution of solar irradiance, and thus can adversely affect PV module performance. In this work, we present an experimental investigation of the distribution of spectral irradiances measured in clear-sky conditions at AM1.5 in Abu Dhabi and assess its impact on the current balance of multijunction PV technologies. High-resolution spectral measurements were obtained using a dual-axis tracked spectroradiometer covering the wavelength range of 300-2500 nm. The results reveal substantial deviations of local spectra at AM1.5 from the standard reference AM1.5 spectrum, along with significant spectral shifts: these shifts were found to induce current imbalances of up to 10% in perovskite/silicon-based multijunction devices. The findings highlight the importance of realistic, location-specific spectral data in the design and optimization of multijunction PV technologies.