Hue and Hoian will enjoy the most pleasant time of year with minimal rainfall. Temperatures will no longer vary much between day and night.
Ho Chi Minh city and Nha Trang are still experiencing fine weather but temperatures tend to go up in the end of the month.
note: this forecast for Vietnam weather in March was drawn from March previous years.
March is a good month to travel in Vietnam, as the weather is fine for the whole country. Reservations are generally not necessary unless you want to settle everything in advance.
You will enjoy reasonable prices plus discounted rates and several fantastic promotional programs for this month.