Southern Vietnam Faces Early End to Rainy Season and Heat Above 39C in 2027 Outlook

Rain could retreat up to 20 days early

Southern Vietnam, including Ho Chi Minh City, is forecast to lose 15 to 20 days of its rainy season as weakening rain systems and a very strong El Niño bring warnings of prolonged heat, water shortages and saltwater intrusion during the 2026-2027 dry season.

Le Dinh Quyet, head of the forecasting division at the Southern Regional Hydro-Meteorological Station, expects the rains to end in early November in Nha Be and the areas formerly administered as Ben Tre, Hau Giang and Soc Trang provinces. Most other southern localities are expected to follow by mid-November. Another regional forecast places the end in the second week of November, 10 to 15 days earlier than the average over many years.

The most serious warnings extend into 2027. Quyet says temperatures in Bien Hoa and Dong Xoai could reach 39 degrees Celsius or higher, with the strongest heat expected in March and April. Rain outside the usual wet season may be scarce between December 2026 and April 2027, leaving fewer opportunities to replenish water supplies.

For the Mekong Delta, the forecast also includes saltwater intrusion beginning as early as late December and reaching its peak between January and April 2027. Its severity could be comparable to the 2015-2016 dry season.

Ho Chi Minh City is already facing an uneven transition: hot afternoons, occasional heavy downpours and tidal flooding can occur while the rainy season is drawing to a close. The practical challenge is preparing for less dependable rain without relaxing precautions against flooding during the remaining storms.

Why the weather systems are weakening

Quyet attributes the early retreat to the weakening southwest monsoon and intertropical convergence zone, two major systems that bring rain to southern Vietnam. Cold air associated with continental high pressure to the north is also expected to become more frequent.

The southwest monsoon carries moist air into the region. The intertropical convergence zone is a belt where winds meet, helping warm, moist air rise and form rain clouds. When both systems weaken, the south loses two important sources of regular rainfall.

The northeast monsoon is becoming dominant, while disturbances that produce rain are fading. An equatorial trough, an elongated area of low pressure, and easterly winds higher in the atmosphere can nevertheless continue supporting scattered showers through the first week of November, including in Lam Dong.

El Niño adds a wider influence. It is a recurring warming of part of the tropical Pacific Ocean that changes air circulation and rainfall patterns far beyond the ocean itself. In southern Vietnam, the forecast links its strong phase to a hotter, drier season. Quyet expects it to peak in November and December, then weaken gradually during the opening months of 2027 while remaining strong.

How forecasters identify the end of the rains

The rainy season ends through a sustained change in rainfall, rather than on the date of the final thunderstorm. The meteorological criteria described by the weather authorities include daily rain below 5 millimetres, a total below 50 millimetres over the following 10 days, and then at least five consecutive days without rain.

A millimetre of rainfall means one litre of water falling on each square metre of level ground. The criteria help forecasters distinguish a brief dry spell from the more lasting shift into the dry season.

Some places in the south and Lam Dong were described as having effectively entered drier conditions between mid and late October. Other areas were still expecting afternoon and evening thunderstorms into early November. The transition therefore moves across the region rather than happening everywhere at once.

October brought heat and heavy downpours

October observations from the Southern Regional Hydro-Meteorological Station show why the transition can feel confusing on the ground. Temperatures were unusually high, yet some locations still received intense rain. Across the southern region, temperatures were reported at 0.5 to 1.3 degrees Celsius above the average over many years; the figure for Ho Chi Minh City was 0.8 to 1.5 degrees above average.

Tan Son Hoa station recorded 35.6 degrees Celsius on October 27. Bien Hoa reached 36.2 degrees on October 1, while Thu Dau Mot recorded a low of 24.1 degrees on October 2. In the cooler highlands, Da Lat recorded 12 degrees on October 26.

Rainfall varied sharply between places. In Ho Chi Minh City, Le Minh Xuan recorded 120 millimetres on October 1, Ben Cat recorded 97.2 millimetres on October 8, and Binh Chanh received 81 millimetres on October 23.

Elsewhere, Vong Dong in An Giang recorded 195.2 millimetres on October 17, Dak Lua in Dong Nai received 181.4 millimetres on October 2, and Dak Mil recorded 158.1 millimetres on October 21. Some locations accumulated 500 to 600 millimetres during the month, while others had a shortfall.

Most monitored areas had rainfall near or above their usual October levels, with Tay Ninh and Vinh Long below average. Those differences matter for the approaching dry season: the amount of water left in fields, ponds and storage facilities depends partly on where the final rains fall.

November rain will be uneven

Ho Chi Minh City is forecast to receive 80 to 180 millimetres of rain during November. In the city centre, rainfall could be 10 to 30 percent below the average over many years. Rain is expected to be more frequent during the first 10 days, then decrease during the middle and end of the month.

The monthly outlook gives different ranges across the south:

• Dong Nai: 60 to 160 millimetres.
• Tay Ninh: 110 to 210 millimetres.
• Can Tho: 50 to 150 millimetres.
• Ca Mau: 100 to 200 millimetres.

Temperatures in Ho Chi Minh City and the wider southern region are forecast to remain 0.5 to 1.3 degrees Celsius above average, with some locations reaching 34 to 36 degrees on hot days. A monthly rainfall total can also conceal long dry gaps interrupted by a few heavy storms.

Showers and tidal flooding can still coincide

The National Center for Hydro-Meteorological Forecasting gave Ho Chi Minh City a 68 percent chance of rain for October 31, with showers potentially increasing between 2 p.m. and 5 p.m. and easing toward evening. Its temperature forecast for that day was 31 to 33 degrees Celsius.

A separate Thursday outlook from the regional weather agency forecast daytime highs of 32 to 35 degrees, with parts of Bien Hoa and Ho Chi Minh City exceeding 35 degrees. Afternoon and evening showers were expected in Lam Dong, Dong Nai, Tay Ninh and Ho Chi Minh City, with thunderstorms potentially continuing late at night in Dong Nai and Tay Ninh. An Giang and Ca Mau were expected to receive the heaviest rain in the Mekong Delta.

The same Thursday outlook put evening high tides at 1.64 metres at Phu An at 8 p.m., 1.67 metres at Nha Be at 7 p.m., and 1.75 metres at Thu Dau Mot at 9 p.m. No calendar date was attached to that Thursday forecast. The agency warned that roads in low lying and riverside areas could remain flooded.

For residents, rainfall and river tides create overlapping problems. A neighbourhood can experience fewer rainy days while still facing inundation when a high tide arrives. Local rain and tide forecasts remain relevant throughout the seasonal change.

Heat is expected to build into March and April

Quyet expects some days of intense heat from mid-February, followed by the main peak in March and April. He described the timing and temperature outlook in these words:

"Hot weather is expected to arrive early, with some days of extreme heat potentially occurring from mid-February," Quyet warned.

The forecasting division head also set out how far temperatures could rise above the usual seasonal level:

The heat is forecast to peak in March and April. Average temperatures could be 1.5 to 2 degrees Celsius above the long-term average.

Bien Hoa and Dong Xoai could reach 39 degrees Celsius or higher. Using 39 degrees as the comparison, that would be 2.8 degrees above the October maximum of 36.2 degrees recorded in Bien Hoa. The comparison shows the scale of the forecast increase between the transition period and the hottest part of the dry season.

A separate regional outlook allows for hot weather as early as December and puts dry season temperatures at 1 to 2 degrees above average. That gives an earlier window for hot spells, while Quyet identifies mid-February as the potential start of intense heat and March and April as the main peak.

Less rain raises water and salinity risks

Quyet warns that severe drought and water shortages could develop during the 2027 dry season. An early end to regular rain would lengthen the period during which households, farms and public water systems must rely more heavily on stored water and river flows.

The forecast of few rain events from December 2026 through April 2027 adds to that concern. Heat increases the loss of water from soil and open water surfaces, while plants need water to keep growing. Occasional showers would provide less dependable relief if dry conditions persist for weeks.

Saltwater intrusion presents a related concern in the Mekong Delta. When freshwater moving downstream becomes insufficient to hold back seawater, salt can travel farther inland through rivers and canals. Water that becomes too salty is harder to use for drinking supplies and many crops.

The salinity outlook places the possible start in late December, followed by a peak from January through April 2027, at a level comparable to the 2015-2016 dry season. Quyet has urged authorities and residents to prepare for extreme heat and drought. For communities dependent on river water, the forecast makes the timing of freshwater storage and checks on salinity especially consequential.

The forecast calendar

The outlook describes a sequence stretching from the final regular rains to the hottest months of the following year. The main periods are:

• Early November: the rainy season may end in Nha Be and the former provinces of Ben Tre, Hau Giang and Soc Trang.
• By mid-November: most of southern Vietnam is expected to finish its rainy season, around 15 to 20 days earlier than usual.
• November and December: El Niño is forecast to reach its peak.
• December 2026 to April 2027: rain outside the usual wet season is expected to be scarce.
• Late December onward: saltwater intrusion may begin in the Mekong Delta, with its peak forecast for January through April 2027.
• From mid-February 2027: some days of intense heat may occur.
• March and April 2027: heat is forecast to peak, with Bien Hoa and Dong Xoai potentially reaching 39 degrees Celsius or higher.

Southern Vietnam therefore faces a transition with two distinct demands: managing the remaining storms and high tides, then conserving freshwater through a potentially longer and hotter dry season. The exact timing varies by locality, with coastal delta areas and Nha Be expected to lose regular rainfall before much of the rest of the region.

Key Points

• Most of southern Vietnam is forecast to end its rainy season by mid-November, about 15 to 20 days earlier than usual.
• Weakening monsoon rain systems and a strong El Niño are central to the regional outlook.
• Ho Chi Minh City could receive 80 to 180 millimetres of rain in November, with showers becoming less frequent later in the month.
• Intense heat may begin in mid-February 2027 and peak in March and April; Bien Hoa and Dong Xoai could reach at least 39 degrees Celsius.
• Few rain events are expected from December 2026 to April 2027, increasing concerns about drought and water shortages.
• Mekong Delta saltwater intrusion could begin in late December and peak between January and April 2027.