Is Vietnam hot in May? The temperature in Vietnam in May is slightly hot, the average temperature is 25 ~33℃. The average temperature during the day is 33℃. I suggest that children wear short tops, short skirts, and light short skirts, light cotton, and other light breathable clothing. The average temperature at night is 25℃. Generally speaking, it is advisable to wear relatively cool and breathable clothes such as cotton and linen shirt, thin long skirts, thin T-shirt wear.