In this paper are presented the results of detailed analyses of remarkable pre-frontal precipitation zones* during a winter season. The analyses are then compared to prefrontal squall-line situations. Then the general aspects of pre-frontal precipitation zones are described in some detail. It is concluded that in the United States to the east of Rocky Mountains, formation of an extensive precipitation zone in a warm sector of a cyclone is a typical phenomenon. It is shown that formations of such extensive pre-frontal precipitation zones are related to regular synoptic scale disturbances aloft rather than a local mechanism which exists only very near to the ground. Roles of static stability are examined and found to be not so important for formations of such organized precipitation systems. It is also pointed out that interaction between the cold frontal surface and the precipitation system may be no more than a secondary importance.