a. Climate
Ha Nam’s weather and climate is hot and humid, the distinctive characteristics of the tropical monsoon climate.
The annual average temperature is around 23-24oC, the average number of hours of sunshine is around 1,300-1,500h/year. Usually 8-9 months of the year have an average temperature of above 20°C (including 5 months with the average temperatures of above 25°C) and only 3 months have the average temperature below 20oC. There is no month in which the temperature reduces to lower than 16oC.
There are two main seasons in a year (summer and winter), with the following prevailing wind directions: south, southwest and southeast wind in the summer; north, east and northeast wind in the winter.
The average rainfall is about 1,900mm, the highest annual rainfall reached 3,176mm (1994), and the lowest annual rainfall was 1,265.3 mm (1998).
The annual average humidity is 85%. There is no month in which the average humidity is below 77%. The average humidity is highest in March (95.5%) and lowest in November (82.5%).
The climate is different in accordance with the temperature regime, with two contrasting seasons being summer and winter and two transition seasons being spring and autumn. Summer lasts from May to September, winter lasts from mid-November to mid-March; Spring usually lasts from mid-March to the end of April and autumn lasts from October to mid-November.
b. Hydrology
Ha Nam has the average rainfall for water resource volume of about 1,602 billion m3. The annual surface flow from Red River, Day River and Nhue River brought roughly 14,050 billion m3 of water into the territory. The underground water flow through the territory also supplies Ha Nam with additional underground water from other areas. Underground water in Ha Nam exists in many layers with good quality, fully meeting the needs for economic and social development.
Many large rivers flow through the territory of Ha Nam, namely Red River, Day River, Chau River and artificial rivers such as Nhue River, Sat River, Nong Giang River, etc.
Red River is the eastern boundary of the province, adjacent to Hung Yen and Thai Binh Provinces. Red River has a length of 38.6 km within the territory of the province. Red River plays an important role in the irrigation and creates fertile alluvial area of nearly 10,000 hectares.
Day River is a tributary of Red River, flowing from Phu Tho to Ha Nam territory. Day River is the boundary between Ha Nam and Ninh Binh. Day River has a length of 47.6 km within the territory of Ha Nam.
Nhue River is a water canal for intake of Red River’s water from the territories of Thuy Phuong, Tu Liem, Ha Noi to Ha Nam with a length of 14.5 km, then pouring into Day River in Phu Ly.
Chau River originates in the territory of Ha Nam. In Tien Phong (Duy Tien), Chau River divides into two branches, one branch acts as the boundary of Ly Nhan and Binh Luc districts and one branch acts as the boundary of Duy Tien and Binh Luc districts. Sat River is a tributary of Chau River in the territory of Binh Luc district.
The above climate and hydrology conditions are very favorable for developing diversified ecological agriculture, with a variety of tropical, subtropical and temperate flora and fauna. The summer has sunshine and heavy precipitation with high temperature and humidity, suitable for all kinds of tropical animals and crops; winter crops have high values with such exports as tomatoes, cucumbers, etc. The weather and climate conditions are favorable for development of industries, trade, tourism, services as well as for social and cultural activities and daily lives of the residents. Many days in the spring and summer have cool weather that is suitable for tourism and festival activities.
