Knowledge of the extent and occurrence of periods when high, and low, attenuation is most likely to occur along slant path links during a typical day is going to be important when planning the design, and use of, future slant path communication systems. This paper presents a statistical analysis of one years measured slant path propagation characteristics at 20 and 40 GHz in southern England; there is a special emphasis on the seasonal and diurnal variations of the attenuation statistics. In particular, the results presented will be of use to system planners who are seeking to make optimal use of low link margin satellite communication systems that incorporate EHF transmissions.