In temperate regions, the zones of contact between relatively warm and cold air masses are known as fronts. Frontal precipitation occurs when the warm and moist air gradually rises above the front created by contact with the wedge of cold air.
In stable air convergence is generally attended by stratiform clouds providing a gray overcast sky and steady long-continued precipitation. However, the principal cause of frontal precipitation is the mixing of air along the fronts.
Frontal precipitation along the warm fronts is usually in the form of drizzle. Another characteristic of this type of precipitation is that it is widespread and of long duration. When associated with cold fronts, it is always in the form of thunder-showers and is of a very short duration.
In Europe and North America, most of the winter precipitation is frontal in origin. Winter precipitation in the northern part of India is a typical example of cyclonic precipitation.