Vietnam is located in both a tropical and a temperate zone. 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 monsoon climate also influences to the changes of the tropical humidity. In general, in Vietnam there are two 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 is almost unnoticeable, averaging 3ºC. The most noticeable variations are found in the northern where differences of 12ºC have been observed. There are essentially four distinct seasons, which are most evident in the northern provinces(from Hai Van Pass toward to the north): Spring, Summer, Autumn, and Winter.
Every year there are 100 rainy days and the average rainfall is 1,500 to 2,000mm. The humidity ranges around 80%. The sunny hours are 1,500 to 2,000 and the average solar radiation of 100kcal/cm2 in a year.
Because Vietnam is affected by the monsoon, that why the average temperature is lower than the other countries which are located in the same longitude in Asia. The annual average temperatures range from 22oC to 27oC. In comparing with these countries, the temperature in winter is colder and in summer is less hotter in Vietnam.
Under influence of monsoon, and further because of the complicated topography, the climate in Vietnam always changes in one year, between the years, or between the areas (from North to South and from low to high). The climate in Vietnam is also under disadvantage of weather, such as typhoons (advantage there are 6-10 storms and tropical low atmosphere in year, floods and droughts are threaten the life and the agriculture of Vietnam).
In Hanoi there are four distinct seasons: Spring, Summer, Autumn, and Winter. But it is able to be divided into two main seasons: the rainy season from May to September (it’s hot, heavy rain), and the dry season from October to April (it’s cold, little rainfall). The annual average temperature is 23.2oC, but in winter the average temperature is 17.2oC. The lowest temperature ever recorded was 2.7oC in 1955. The average summer temperature is 29.2oC, with the highest ever recorded being 42.8oC in 1926. On average, there are 114 rainy days a year with around 1,800mm of rainfall.
Three quarters of Vietnam's territory consists of mountains and hills. Vietnam is divided into four distinct mountainous zones.
The Northeastern Zone (Viet Bac)
This zone stretches from the Red River Valley to the Gulf of Tonkin. The mountainous area of Viet Bac is scattered with famous sights: Dong Nhat Grotto, Dong Nhi Grotto, and Tam Thanh Grotto in Lang Son Province; Pac Bo Grotto and Ban Gioc Waterfall in Cao Bang; Ba Be Lake in Bac Kan; Yen Tu Mountain and Halong Bay in Quang Ninh; and Tay Con Linh, the highest mountain peak in the region reaching 2,341 meters above sea level.
The Northwestern Zone
This zone is comprised of mountains that run from the north of the Sino-Vietnamese border to the west of Thanh Hoa Province. This magnificent mountain range is nationally known for its resort town of Sapa in Lao Cai Province, which is perched 1500 meters above sea level. Several ethnic groups, such as the H'mong, Dao, Kinh, Tay, Giay, Hoa, and Xa Pho, still reside in this region.
The northwestern zone is also famous for the historical site of Dien Bien Phu and Fansipan Mountain, which measures 3,143 meters above sea level at the peak.
The North Truong Son Zone
This zone runs from the western part of Thanh Hoa Province to the Quang Nam-Da Nang Mountains. This region is known locally for its picturesque Phong Nha Grotto and its two breathtaking passes, the Ngang Pass and the Hai Van Pass. It is also known worldwide for being the location of the legendary Ho Chi Minh Trail constructed during the second great resistance war.
The South Truong Son Zone
This zone is located to the west of the south central coast provinces. Behind these huge mountains is a vast area of red soil known locally as Tay Nguyen (the Central Highlands). There are numerous legendary accounts of the flora and fauna and of the lives of several different ethnic minorities living in the Central Highlands. Dalat, established during the 19th century, is a popular resort town in this part of Vietnam.
Vietnam has two major deltas, including the Red River Delta in the north and the Mekong River Delta in the south.
The Red River Delta, or Northern Delta
This region stretches for15,000 sq. km. Over time, deposits of alluvium carried from the Red River and Thai Binh River have accumulated to form the delta. The ancient Viet people settled at the junction of the two rivers . At that time, the wet rice civilization was established
The Mekong River Delta, or Southern Delta
This region is approximately 40,000 sq. km. The land is very fertile and has favorable climate conditions for agriculture. As a result, it is the largest rice growing region in Vietnam.
Vietnam is crisscrossed by thousands of streams and rivers. There is a river discharging every 20 kilometers along Vietnam's coastline. The waterways are a very convenient means of transport with major rivers like the Red River in the north and the Mekong River in the south.
Vietnam's coastline is 3,260km long. If you have a chance to travel along the coast of Vietnam, you will be able to enjoy the beautiful beaches of Tra Co, Sam Son, Lang Co, Non Nuoc, Nha Trang, Vung Tau, and Ha Tien. In some places, you will see mountains jutting out to the sea. One such magnificent site is Halong Bay, which has recently been listed as a World Heritage Site by UNESCO.
Vietnam's coast has been awarded a series of large seaports, such as the ones at Haiphong, Danang, Qui Nhon, Cam Ranh, Vung Tau, and Saigon. There are thousands of islands and islets scattered offshore from north to south. Among the most popular tourist destinations are the Truong Sa and Hoang Sa Archipelagos.
The forests of Vietnam account for most of the total land area. National parks are preserved by the state and follow a steady development plan. Some of the more famous national parks located throughout the country include Ba Vi in Ha Tay, Cat Ba in Haiphong, Cuc Phuong in Ninh Binh, Bach Ma in Hue, and Cat Tien in Dong Nai.