Entry Requirements: You must have a valid passport and a visa (or pre-approval for a visa on arrival) to enter Vietnam. Your passport must be valid for 06 months beyond your planned stay, and you must have at least one blank visa page. Visit the Embassy of Vietnam website for the most current information. If you arrive in Vietnam without an appropriate visa (which could be an e-visa) or pre-approval for a visa on arrival, you will be denied entry.
Visas: When you apply for a visa to enter Vietnam, be sure to request the visa category that corresponds to your purpose of travel. Please refer to Vietnam’s Ministry of Foreign Affairs website for information detailing visa categories. If you plan to work in Vietnam, you must obtain a work permit before applying for your visa. If you change the purpose of your visit after you have received your visa, you must obtain a new visa outside of Vietnam appropriate for your new activities before beginning those activities. Please consult the Embassy of Vietnam website for more information.
Travel by land: If you plan to travel to Vietnam from Cambodia or Laos by land, an adhesive visa must be affixed to your passport. Approval letter for visa on arrival is invalid and not acceptable. If you travel from Vietnam to Laos by land, you should request that an adhesive visa be affixed to your passport instead of a detachable one. Lao immigration officials require proof that travelers have departed Vietnam, something that can only be shown with an adhesive visa. Vietnamese officials remove detachable visas from passports when travelers depart Vietnam, leaving travelers with no proof of their Vietnam departure. This situation can result in Lao officials requiring travelers to return to Vietnam.
Pre-approval for Visa on Arrival: The Government of Vietnam has authorized some businesses and travel agencies to arrange for pre-approval for a “visa on arrival” at the airport. This is the most convenient and cheapest way and the application fee costs around 10 USD/person excluding stamping fee of 20$ to 30 USD/person that client will have to pay upon landing at the airport. Travelers are recommend to obtain a visa directly from an embassy or consulate of Vietnam prior to arrival.
E-visa: Travelers in some countries can now apply online for a single entry E-visa on the Vietnam Immigration website. The E-visa is valid for a maximum of 30 days for the purpose of tourism. An E-visa is usually processed within three working days after the Vietnam Immigration Department receives the completed application and E-visa fee. E-visa holders must present the printed E-visa and valid passport at the port of entry. Prior to making travel arrangements with an E-visa it is advisable to review the List of Ports of Entry that allow for foreigners to enter and exit Vietnam by E-visa. When applying for an E-visa, carefully review and follow the E-visa application steps. (Source: Used and re-edited from travel.state.gov)
Southern Vietnam: In southern Vietnam the dry season lasts from December to late April or May, and the rains from May through to November. Since most rain falls in brief afternoon downpours, this need not be off-putting, though flooding at this time of year can cause problems in the Mekong Delta. Daytime temperatures in the region rarely drop below 20°C, occasionally hitting 40°C during the hottest months (March, April and May). The climate of the central highlands generally follows the same pattern, though temperatures are cooler, especially at night. Again, the monsoon rains of May to October can make transport more complicated, sometimes washing out roads and cutting off remoter villages.
Central Coast: Along the central coast the rainfall pattern reverses under the influence of the northeast monsoon. Around Nha Trang the wet season starts with a flourish in November and continues through December. Further north, around Hué and Da Nang, the rains last a bit longer, from September to February, so it pays to visit these two cities in the spring (Feb–May). Temperatures reach their maximum (often in the upper 30s) from June to August, when it’s pleasant to escape into the hills. The northern stretches of this coastal region experience a more extreme climate, with a shorter rainy season (peaking in Sept and Oct) and a hot dry summer. The coast of central Vietnam is the zone most likely to be hit by typhoons, bringing torrential rain and hurricane-force winds. Though notoriously difficult to predict, in general the typhoon season lasts from August to November.
Northern Vietnam: Northern Vietnam is generally warm and sunny from October to December, after which cold winter weather sets in, accompanied by fine persistent mists which can last for several days. Temperatures begin to rise again in March, building to summer maximums that occasionally reach 40°C between May and August, though average temperatures in Hanoi hover around a more reasonable 30°C. However, summer is also the rainy season, when heavy downpours render the low-lying delta area almost unbearably hot and sticky, and flooding is a regular hazard. The northern mountains share the same basic regime, though temperatures are considerably cooler and higher regions see ground frosts, or even a rare snowfall, during the winter (Dec–Feb).
Best time to go: With such a complicated weather picture, there’s no one particular season to recommend as the best time for visiting Vietnam. Overall, autumn (Sep-Dec) and spring (March and April) are probably the most favourable seasons if you’re covering the whole country. (Source: RoughGuide)
There are six international airports in Vietnam. Others, including Hue, are officially classified as 'international' but have no overseas connections (apart from the odd charter). Except for two major airports are Hanoi and Ho Chi Minh City where many airlines have direct flights to and from, you can check out the list of major international airports as follow: