There is no perfect time to visit Vietnam. Generally speaking, destinations in the north such as Hanoi and Sapa are great in October, November and December, as you'll see little rain and should have clear skies and temperate conditions.
The coastal stretch from Hue down to Nha Trang is great in the first half of the year, from January through to July, while Saigon and the Mekong Delta are best from November through to February or March.
