The climate of Vietnam varies greatly from one region of the country to another. The south of Vietnam is a mere 8 degrees north of the Equator, whereas the most northern point is almost on the tropic of Cancer. One can't really say that there is one average temperature for all of the country because it is so variable. Most of Vietnam has a sub tropical climate and is hot, at least in the summer, and wet most of the year.
Southern Vietnam experiences very little seasonal temperature change. It has a tropical, hot and humid, climate, and has only two real seasons - the monsoon season and the dry season. The monsoon season brings lots of rain, heat, and regular floods. All of Vietnam is affected by monsoons from May until October or November. The average yearly temperature for this southern region is around 80 or 90 degrees F (27-32 degrees C). Northern Vietnam, along the Red River, has hot, wet summers (80-90 F, 27-32 C), similar to those in the south. Winters, lasting from November to April, are drier and much cooler, with temperatures in the 40's and 50's (F) (5-10 degrees C). Winters have scattered showers. The mountainous regions of Vietnam, between the two lowland deltas, and forming a northern border between Vietnam and China are generally cooler. They still get lots of rain, and jungle plants still abound. The mountains, and the coastal areas are subject to seasonal typhoons. Average annual rainfall for Hanoi (north) is about 80 inches ?. For Ho Chi Minh City (south) it is about 60 inches ?. Hue, near the central coast gets about 120 inches per year.
The climate in Southern Vietnam is excellent for growing rice. Rice is grown all over, but mainly in the northern and southern deltas. The mountains, with cooler temperatures, and poorer soil, are used to grow cash crops such as rubber, coffee and even a form of poppy used to make heroine. The people in Vietnam are prepared for all that the weather brings them. They expect and need the rains to supply water to their rice, and have built dikes to help protect their homes from flooding. To combat the sun and heat, most Vietnamese can be seen wearing conical hats, and staying indoors or in the shade during the hottest hours of the day.