· Vietnam is approximately 331,688 km² (128,066 sq mi) in area (not including Hoang Sa and Truong Sa islands), larger than Italy and almost the size of Germany. The perimeter of the country running along its international boundaries is 4,639 km (2,883 mi).
· The topography consists of hills and densely forested mountains, with level land covering no more than 20%. Mountains account for 40% of the area, with smaller hills accounting for 40% and tropical forests 42%. The northern part of the country consists mostly of highlands and the Red River Delta. Phan Xi Păng, located in Lào Cai province, is the highest mountain in Vietnam at 3,143 m (10,312 ft).
· The south is divided into coastal lowlands, Annamite Chain peaks, extensive forests, and poor soil. Comprising five relatively flat plateaus of basalt soil, the highlands account for 16% of the country's arable land and 22% of its total forested land.
· Topography of Vietnam.The delta of the Red River (also known as the Sông Hồng), a flat, triangular region of 15,000 km2 (5,792 sq mi), is smaller but more intensely developed and more densely populated than the Mekong River Delta. Once an inlet of the Gulf of Tonkin, it has been filled in by the enormous alluvial deposits of the rivers over a period of millennia, and it advances one hundred meters into the Gulf annually. The Mekong delta, covering about 40,000 km2 (15,444 sq mi), is a low-level plain no more than three meters above sea level at any point and criss-crossed by a maze of canals and rivers. So much sediment is carried by the Mekong's various branches and tributaries that the delta advances sixty to eighty meters into the sea every year.
· Because of differences in latitude and the marked variety of topographical relief, the climate tends to vary considerably from place to place. During the winter or dry season, extending roughly from November to April, the monsoon winds usually blow from the northeast along the China coast and across the Gulf of Tonkin, picking up considerable moisture; consequently the winter season in most parts of the country is dry only by comparison with the rainy or summer season.
· The average annual temperature is generally higher in the plains than in the mountains and plateaus and in the south than in the north. Temperatures in the southern plains (Ho Chi Minh City and the Mekong Delta) varies less, going between 21 and 28 °C (70 and 82.5 °F) over the course of a year. The seasons in the mountains and plateaus and in the north are much more dramatic, and temperatures may vary from 5 °C (41 °F) in December and January to 37 °C (98.6 °F) in July and August.
Vietnam is located in both a tropical and a temperate zone.meteo_du_vietnam It is characterized by strong monsoon influences, but has a considerable amount of sun, a high rate of rainfall, and high humidity. Regions located near the tropics and in the mountainous regions are endowed with a temperate climate.
The annual average temperature ranges from 22ºC to 27ºC. In Hanoi, the average temperature is 24ºC, in Ho Chi Minh City it is 27ºC, and in Hue it is 26ºC.
There are two distinguishable seasons. The cold season occurs from November to April and the hot season from May to October. The difference in temperature between the two seasons in southern Vietnam is almost unnoticeable, averaging 3ºC. The most noticeable variations are found in the northern provinces where differences of 12ºC have been observed. There are essentially four distinct seasons, which are most evident in the northern provinces.
North: In the highlands Nov-Mar, it is very cold, especially mornings. Jacket necessary.
South: T-shirts are enough all year around, except in the highlands, where it can be cooler. Apr-May is very hot. Hats are essential to avoid sun stroke.
Advice: Best season to travel in Vietnam: from November to May. vietnam travel