Results are presented describing the cumulative fading distribution determined over 3 consecutive years during the fading season (June-August) on a 51-km terrestrial microwave link. The fading is more severe at low signal levels than expected from the International Radio Consultative Committee predictions based on accumulated data from many such links over the years. An attempt is made to isolate the cause of the deep fading in terms of the atmospheric processes involved.¿ 1997 American Geophysical Union