El Niño could reach very strong intensity.
According to Mr. Nguyen Duc Hoa, Deputy Head of the Climate Forecasting Division at the National Center for Hydro-Meteorological Forecasting, weather conditions across the country were complex from June to mid-August 2026, characterized by widespread heatwaves, thunderstorms, tornadoes, lightning, and hail, alongside the activity of typhoons and tropical depressions.
During this period, two tropical depressions and three typhoons were recorded in the East Sea. Notably, Typhoon No. 1 (Maysak) formed in early July, intensifying to Level 9 with gusts at Level 11; it subsequently made landfall near Mong Cai (Quang Ninh) on the evening of July 4 with sustained winds at Levels 8–9 and gusts at Level 12, before weakening over land.
Northern and Central regions experienced multiple heatwaves. Numerous meteorological stations recorded temperatures exceeding historical highs for the corresponding periods; specifically, historical records were surpassed at 22 stations in June, two stations in July, and nine stations during the first half of August.
Mr. Hoa stated that ENSO conditions are currently in an El Niño phase. During the second week of August 2026, the sea surface temperature anomaly in the NINO3.4 region reached 1.8°C.
Forecasts indicate that from September to November 2026, El Niño will maintain strong to very strong intensity with 100% probability, with a 93% likelihood of reaching "very strong" status. For the October–December 2026 period, the probability of a "very strong" El Niño rises to 95%. From December 2026 through February 2027, there remains a 93% probability that the phenomenon will sustain strong to very strong intensity.
High temperatures; fewer episodes of severe cold
Meteorological agencies forecast that in September 2026, the average temperature nationwide will be 0.5–1.5°C higher than the long-term average. In October and November, the deviation is expected to generally range from 1°C to 2°C, with some areas experiencing even higher anomalies.
From December 2026 to February 2027, temperatures are expected to remain 0.5–1.5°C above the long-term average, with the Central Highlands and Southern regions potentially seeing anomalies of 1.5–2°C.
Notably, cold air activity is forecast to be weaker than the long-term average. Between December 2026 and January 2027, episodes of severe cold are likely to arrive late, and the total number of cold days is expected to be lower than climatological norms. However, this does not mean winter weather will be consistently warm. When strong cold air masses arrive, severe cold spells, damaging cold, frost, or ice can still occur, impacting both public health and agricultural production.
Complex rainfall patterns: Surplus in some areas, severe deficits in others
In September, total rainfall in the Northern and Central regions is forecast to be 10–30% below the long-term average, while other areas will see levels close to the average.
In October, rainfall in the Northern region is expected to be 5–20% above average, whereas many other areas will see levels 5–20% below average. Notably, the region stretching from southern Nghe An to Da Nang and the South Central Coast could face a deficit of 20–40%.
In November, the Northern region and the area from Thanh Hoa to Ha Tinh will likely experience rainfall 10–30% above average. Conversely, the region from Quang Tri to Lam Dong could see levels 20–40% below average, and the Southern region 5–15% below average.
By December, the Northern region and the area from Thanh Hoa to Ha Tinh will continue to see rainfall trends above average. Meanwhile, the South Central Coast could face a deficit of 40–100mm.
During January and February 2027, rainfall across most regions is forecast to be 5–20mm below average, while the Northern region will remain close to the average.
Meteorological agencies warn that the region from Ha Tinh to Hue and the South Central Coast face a risk of rainfall deficits during the peak rainy season months, particularly October and November.
In the Central Highlands and the Southern region, the rainy season is likely to end early. During January and February 2027, these two regions may experience periods of low rainfall, placing strain on water supplies and agricultural production. Fewer storms, but potential for extreme weather
From September 2026 to February 2027, the activity of storms and tropical depressions over the East Sea—as well as the likelihood of them making landfall in Vietnam—is forecast to be below the long-term average. Historically, this period sees an average of 7.3 such systems active over the East Sea, with 3.1 making landfall.
Specifically, between September and November 2026, approximately 3–5 storms or tropical depressions are expected to be active over the East Sea, with about 1–2 making landfall; these figures are lower than the long-term averages (5.9 active systems and 2.9 landfalls).
Nevertheless, widespread moderate to heavy rainfall remains possible during September and October. During this transitional season, thunderstorms, tornadoes, lightning, and hail may occur in many areas.
Meteorological authorities advise the public and local authorities to actively monitor forecasts, particularly in areas at risk of rainfall deficits, localized heavy rain, or impacts from strong cold air surges.