I know that there are differences in climate areas along the length of Vietnam -- the northern provinces can get colder, especially in the winter months. For most of the year, though, it seems to be quite balmy. And Ho Chi Minh City stays warm almost all year -- even throughout the rainy season.
Therefore life in Vietnam is lived outdoors. The homes have lots of openings, and relaxation takes place outside the entries to the homes -- usually on the street because that is where the extra space is. Certainly all street food is consumed on short stools on the sidewalk or street, and most restaurants have terraces or balconies.
Here on vacation in Branson, Missouri this week, the temperatures have been in the 30s to 60s (0 to 16C), so life is lived indoors in restaurants or show halls. The same usually applies in San Francisco where the average temperature is in the 50s or 60s (12 to 17C) -- there are some good days for sidewalk cafes, but nowhere near enough.
I really like the outdoor living, and can hardly wait to get back to Vietnam in a few weeks. And I do like the heat and hate the air-conditioning.