The rainy season in the Central Highlands and southern regions of Vietnam is starting later than usual this year, with the southeast provinces and cities forecast to receive rain first.

The southern hydro-meteorological station reported that while the rainy season typically begins in late April to early May each year in southern Vietnam, it is expected to start between May 10 and 20 this year.

From May 10 to 15, the rainy season will commence in several places, including the southeast provinces and cities, except Ba Ria-Vung Tau Province, followed by the Mekong Delta provinces of Ca Mau, Kien Giang, and Hau Giang. 

The provinces of Ba Ria-Vung Tau, Tien Giang, and Ben Tre will experience the onset of the rainy season later. 

It is expected that the entire southern region will enter the rainy season from May 17 to 22.

The first half of May marks the transition from the dry season to the rainy season, characterized by dangerous weather phenomena such as thunderstorms, whirlwinds, and especially heavy rains and lightning. 

This period will provide relief from the prolonged hot weather in the Central Highlands and the south. 

Starting in June, the southwest monsoon is likely to strengthen, increasing the likelihood of rain.

“The rainy season in the southern provinces is significantly influenced by the activity of the southwest monsoon, which originates from the sea and forms over areas with high sea surface temperatures,” said Le Dinh Quyet, head of the weather forecast division under the southern hydro-meteorological station. 

“This monsoon brings hot, humid air masses laden with abundant moisture, resulting in rainfall over the mainland.”

Drought, water shortages expected in northern, central regions

Hoang Phuc Lam, deputy director of the National Center for Hydro-meteorological Forecasting, said that the El Nino phenomenon, which has caused temperatures across Vietnam to be 0.5-2 degrees Celsius higher and rainfall levels lower than the average of previous years, will persist over the next three months, from May to July, but its intensity will gradually weaken. 

Afterward, it is likely to transition to a neutral state with a 75-80 percent probability.

Currently, the hot depression in the west is gradually strengthening, causing temperatures in the northern region and provinces and cities from Thanh Hoa to Phu Yen to rise from May to July. 

“This year, hot weather and intense heat are likely to occur more frequently than usual during this period,” Lam cautioned. 

He added that the onset of the rainy season in the northern and central regions is expected to align with the typical time frame observed over many years.

Lam also noted that from May to July, rainfall in the north should match the average levels seen in past years. 

The scant rainfall combined with increased heat will lead to lower water levels in major rivers and reservoirs in the northern region during these three months. 

For instance, the flow to large reservoirs on the Da River will be 30-40 percent below average, although Hoa Binh Lake may see higher levels in May due to upstream water releases. 

The flow to Thac Ba Lake from the Chay River and Tuyen Quang Lake from the Gam River is expected to be 20-30 percent below the norm.

In the central region, rainfall in May will be generally 10-30 percent below the multi-year average. 

By June, precipitation should align with typical levels.

In July, rains in the north-central region should meet the annual average, while the central and south-central regions may see a 15-30 percent increase.

The central region could face drought conditions lasting from the latter half of this month through July. 

Water levels on rivers in the central region will change slowly in late April and May, with more significant fluctuations forecast for June and July in the upper reaches of rivers in Thanh Hoa and Nghe An Provinces, whereas other rivers will see slower changes.

Flow rates on rivers in Thanh Hoa Province, the Ta Trach River in Thua Thien-Hue Province, the Tra Khuc River in Quang Ngai Province, and rivers in Binh Dinh, Khanh Hoa, and northern Binh Thuan Provinces will be approximately 10-30 percent higher than the average for many years. 

However, other rivers will experience flow rates 15-55 percent lower than the multi-year average.

Specifically, the Ben Hai River in Quang Tri Province, the Ba River in Phu Yen Province, and the La Nga River in Binh Thuan Province will see significant reductions, with flow rates 65-80 percent below the long-term average.

“From May to July this year, drought and water shortages will affect provinces from Quang Tri to Quang Nam, and from Phu Yen to Binh Thuan, especially in areas outside the water supply zones of irrigation projects,” Lam noted.

Lam’s meteorological agency also predicted that the number of storms and tropical depressions in the East Vietnam Sea from now until July will be below the multi-year average, with an expected two to three storms.

Like us on Facebook or follow us on Twitter to get the latest news about Vietnam!