North: Winter lasts from November to April with temperatures averaging 10°C—16°C, with fog and drizzle January-March. Summer begins in May and lasts until October, with an average temperature of 30°C with heavy rainfall and the occasional violent typhoon.
Center: Central Vietnam experiences a transitional climate, with heavy rainfall between November and December and dry, hot summer months. Typhoons are quite common in coastal areas between July and November.
South: Temperatures are fairly constant through the year: 25°C—30°C. Seasons are determined by the rains. The dry season runs from November to April and the wet season from May to October. The hottest period is in March and April.
Highland areas: In the hill resorts of Dalat (1,500 m), Buon Me Thuot and Sapa, nights are cool throughout the year. In the winter months, October to March, it can be distinctly chilly with temperatures falling to 0°C. Even in the hottest months of March and April the temperature rarely exceeds 26°C.
Cambodia can be visited throughout the year. However those planning to travel extensively by road should avoid the last two months of the rainy season when some countryside roads may be impassable.
The climate can generally be described as tropical. As the country is affected by monsoons, it is hot and humid with an average temperature of around 27°C (80°F) but in the dry season it is cool and very much like a European summer.
There are two distinct seasons: the Rainy Season and the Dry Season. However, the Dry Season is divided into two sub-seasons—cool and hot—and these seasons are:
- The Rainy Season : from June till October 27-35°C (80-95°F)
- The Dry Season (cool): from November till February 17-27°C (80-95°F)
- The Dry Season (hot) : from March till May 29-38°C (84-100°F)
In Vientiane a minimum temperature of 19°C is to be expected during January. In mountainous areas, however, the temperature drops to as low as 14-15°C during the winter months, and during cold nights, it can easily reach the freezing point. The average precipitation is the highest in Southern Laos, where the Annamite Mountains receive over 3,000 mm annually. In Vientiane rainfall is about 1,500-2,000 mm, and in the northern provinces only 1,000-1,500 mm.