Dust storms are significant meteorological phenomena which attenuates signal level especially at Ku band and higher frequencies with direct impact on telecommunications system performance. Few prediction models have been developed to calculate the attenuation due to dust storm in dB/km. All prediction models have assumed that the intensity of dust storm is uniformly distributed around the area covered by the dust storm. It has been found that the dust storm intensity is not uniformly distributed along the horizontal path. However, to predict the total attenuation due to dust storm that a microwave link might suffer, an adjustment factor is needed to account for the variation of dust storm intensity along the propagation path. In this paper an adjustment factor which reflects the variation of dust storm horizontally (terrestrial links) has been derived based on the analysis of the horizontal dust storm behavior. It has been found that the estimated attenuation with the horizontal adjustment factor is very close to the measured attenuation than without using the horizontal adjustment factor.