Vietnam: Weather and what to expect
Ho Chi Minh City has a tropical climate and to me is hot January to December. It has the best weather to me, during the months of December to April because this is the dry season. You will experience less humidity if any and less rain. The temperatures tend to be more comfortable for sightseeing all day and night.
You will experience more milder weather around the months of December to February.
Still, I would keep that rain jacket close by just incase.