May is summer in the North and in the Central Region of Vietnam, and rainy season in the Central Highlands and South of Vietnam.

1/ Winds Affecting Vietnam in May 

The winds which affect Vietnam in May include the southeasterly wind and southwesterly wind. Both of these winds are moist, but for the southwesterly wind when it comes to the Central Coast and the extreme Northwest of Vietnam it becomes dry and hot due to the foehn effect, hence dry and high temperatures in the affected regions.

2/ The North of Vietnam

In the North of Vietnam, May is the beginning of the summer which means high temperatures (28-35oC) and occasional thunderstorms. Typhoons, tropical depressions and flash floods in the mountains may be found in May but not often.

- The Northeast of Vietnam enjoys quite pleasant temperatures in May, 22-30oC. But the Northeast has more rainfalls than the other regions of Vietnam due to that the northeasterly wind comes from the sea and it is moist and cool. The occasional rains last for only a couple of hours.

Halong Bay on a day in May

- The Northwest of Vietnam has two sub-regions with slightly different weather patterns.

+ The region in between the extreme Northwest and the Northeast (which includes Hoa Binh, Yen Bai and Lao Cai) tend to have more pleasant temperatures than the extreme Northwest but higher temperatures than most of the low lands. The reason is that a part of this region (in Hoa Binh and especially in Lao Cai) is affected by the foehn wind. The temperatures are 24-33oC.

Van Chan Yen Bai in May

Sapa is on high altitude with cool temperatures, 14-21oC mostly and with rains often. Mu Cang Chai often has thunderstorms, 20-27oC.

+ The extreme Northwest of Vietnam (which includes Son La, Dien Bien and Lai Chau) is strongly affected by the foehn wind which makes the air dry and hot. The temperatures are 26-35oC. It rains less here than the inner Northwest. The extreme Northwest is more vulnerable to the foehn effect and it often suffers the most from heat strikes which make daily temperatures very high from 38-41oC.

Moc Chau Plateau normally enjoys lovely day with mild sunshine, some short-lived thunderstorms are possible, 20-26oC.

- The lowlands (including Quang Ninh – Halong Bay, Hai Phong, Thai Binh, Nam Dinh, Ninh Binh, Hanoi) tend to receive more of the northeasterly wind which makes the air more pleasant than the Northwest but short-lived thunderstorms are found more often too. The temperatures are 25-32oC.

The Tieu Son Pagoda in Bac Ninh in May

3/The North of the Central Region of Vietnam

This region is dry and tend to have high temperatures due to that the region is influenced by the foehn wind. The temperatures are 28-35oC but heat strikes come often and they tend to make the temperatures high from above 28oC to above 36oC. There are occasional thunderstorms in May in this region.

4/The Central Coast of Vietnam 

This region can be divided into 3 sub-regions:
- North of the Hai Van Pass (Quang Binh, Quang Tri, Thua Thien Hue) is in strong influence of the foehn wind with high daily temperatures from 28 to above 37oC.

- South of the Hai Van Pass (Da Nang Beach, Quang Nam - Hoi An, Quang Ngai, Binh Dinh - Quy Nhon Beach, Phu Yen - Tuy Hoa Beach) is like the Central Coast to the north of the Hai Van Pass under strong influence of the foehn wind with high temperatures from 28-37oC.

The regions to the north and south of the Hai Van Pass while tend to have high temperatures in May but with different influencing factors that make the weather patterns (temperatures, rainfalls, …) different at a time.

- South of the Central Coast ( Khanh Hoa - Nha Trang Beach, Ninh Thuan - Ninh Chu Beach and Binh Thuan - Mui Ne Beach) enjoys more pleasant temperature than all the other regions in the Central Coast. There are occasional thunderstorms in May and the temperatures are 28-34oC. This region does not often suffer from heat waves or heat strikes.

5/ The Central Highlands of Vietnam

The Central Highlands are in the rainy season in May with daily short-lived rains, mostly cloudy skies and lovely temperatures, 22-31oC. It does not get warm in the region in May, if any, then the high temperatures are found at mid day mostly for a couple of hours. It is normally chilly in the early morning and afternoon and evening.

6/The South of Vietnam

The South of Vietnam is in the rainy season in May, it is more often with clouds or mild sunshine. And the temperatures are stable and basically similar all over the region, 26-34oC. There are daily rains which make streets in cities temporarily flooded. Exercise caution when traveling on flooded streets as fatal accidents have been reported due to strong currents and openings of the sewage system. There may be strong winds sometimes and it is good to pay attention to falling tree branches, banners, posters...

The Con Dao Islands and Phu Quoc Islands are both in the rainy season in May with occasional thunderstorms, cloudy skies, 28-31oC.