Situated between the Tropic of Cancer and the Equator, Viet Nam has a tropical climate. Annual average temperature is over 68° F (20° C) throughout the country except on the mountain peaks and in certain low valleys in the plateau region. It runs between 68° F (20° C) in December and 86° F (30° C) in June. The temperature begins to decline in July and reaches its minimum at the end of the winter.

Viet Nam is a humid country. On the average, she receives more than 1,500 m/m of rainfall a year in the plains, and from 2,000 to 3,000 m/m on the mountains. The average relative humidity varies between 70 and 90%. It never snows in Viet Nam, except for the area of Chapa, located on the northern border with China.  Such climate favors vegetation throughout the year and would allow 2 or 3 crops per year with proper irrigation. Rivers with an abundant flow make up a dense hydrographic network.

The Red River and the Mekong River, the biggest ones, discharge respectively 122,109 meters and 1,400,109 cubic meters of water a year. The volume of silt deposit reaches a billion of cubic meters per year. At the mouth of the Mekong, and around the Ca-Mau peninsula, this silt increase the amount of mud in territory of South Viet Nam by encroaching on the sea at the rate of about 80 meters per year.

The rich soil, humid and red or yellow in color resulting from the decomposition of basalt is most fertile. The fifth of the territory are covered by vast natural forests (not including rubber plantation). Dense tropical forests prevail. The fauna and the flora show great variety. The fauna is abundant and comprises over 200 species of mammals, among the big ones, elephant, tiger, panther, bear, gaur, wild buffalo and stag. 1,000 species of birds inhabit the forests, some of which are renowed for their plumage: peacocks, pheasants, parrots... others for their song: larks, blackbirds... The seas, lakes, rivers, canals swarm with 200 species of fresh water fish and nearly 800 species of sea fish.