I find different recommendation on different sites. I want to see what everyone says here. I have always wanted to experience the snow in Vietnam. I heard it was like that of a snow globe with biog fluffy snowflakes that sparkle.
You have to go far up into the mountains to experience the snow. I am not sure where you would go or stay but it would have to be in the winter months for sure.
You have two options that I know of. Tam Dao and Mau Son (Lang Son). Both experience snow but it isn't like way up in the mountains. Nothing like you would experience in Canada, for example. You won't be buried in the stuff. It is still beautiful when lightly coated in snow and ice in both areas. December and January is your best bet.
Snox in Vietnam ? FUNNY ! It snows on top of the Fan Si Pan Mountain in Sapa (over 3000-m altitude), generally in February, and it snowed last winter in Sapa itself, (1500 meters), the first time in fifty years
Both places mention get snow but you may not see any at all on your trip. It is hard to plan for something like this. Vietnam is not the place to go to if you want to see snow!
I have seen pictures and videos of the snow and while it is beautiful, it is very rare unless you live int he mountains as mentioned. I have gotten to experience it once but I have family that lived way up north at the time and I was young. They have since moved.