South Vietnam lies entirely below the Tropic of Cancer. Its climate is best described as hot and humid. Because the country is situated within Southeast Asia’s twin tropical monsoon belt, it experiences two distinct rainy seasons. The southwest (or summer) monsoon settles over the Mekong Delta and the southern part of the country in mid-May and lasts until early October. In the northern reaches, the northeast (or winter) monsoon season begins in November and continues through most of March. Unlike the rainy season in the south, fog, wind, and noticeably lower temperatures characterize the wet season in the north. While the reversed monsoon seasons provide an abundance of water for rice growing throughout the Mekong Delta and most of the long coastal plain, rainfall is not distributed uniformly. Parts of the central coast record only about 28 inches of annual precipitation. In contrast, other areas along the northern coast receive as much as 126 inches of rain during the course of a year. Even worse, a percentage of this rainfall can be expected to occur as a result of typhoons. The tropical storms usually lash the Annamese coast between July and November. Almost always they cause extensive flooding along normally sluggish rivers which dissect the coastal plain. _The People_ Slightly over 16 million people currently inhabit South Vietnam. Of these, over 13 million are ethnic Vietnamese. Primarily rice farmers and fishermen, the Vietnamese have tended to compress themselves into the country’s most productive agricultural areas--the Mekong Delta and the coastal plain. Chinese, numbering around one million, form South Vietnam’s largest ethnic minority. Concentrated for the most part in the major cities, the Chinese traditionally have played a leading role in Vietnam’s commerce. About 700,000 Montagnard tribesmen, scattered across the upland plateau and the rugged northern mountains, constitute South Vietnam’s second largest minority. Some 400,000 Khmers, closely akin to the dominant population of Cambodia, inhabit the lowlands along the Cambodian border. Roughly 35,000 Chams, remnants of a once powerful kingdom that blocked the southern migration of the Vietnamese until the late 1400s, form the country’s smallest and least influential ethnic minority. The Chams, whose ancestors once controlled most of the central and southern Annamese coast, are confined to a few small villages on the central coast near Phan Rang. [Illustration: TERRAIN FEATURES SOUTH VIETNAM ]