ENSO is one of the large-scale factors dominating summer temperatures in Vietnam. When El Nino occurs, hot sun tends to appear more, last longer, and be more intense. Conversely, in the La Nina phase, hot sun is usually less and not too harsh. However, ENSO mainly adjusts the general trend of summer, while specific heat waves still depend on regional weather systems such as the hot low pressure in the west or the foehn effect.
Reporters had an interview with Mr. Nguyen Van Huong - Head of Weather Forecast Department, National Center for Hydro-Meteorological Forecasting about the summer 2026 trend forecast information.
Sir, what is the trend of the ENSO phenomenon in 2026?
- Currently, ENSO is in a weak La Nina state with the central Pacific regional sea surface temperature deviation (NINO3.4) in the last week of February 2026 at around -0.6 degrees Celsius.
However, forecast models show that in the next three months, ENSO is highly likely (80 - 90%) to gradually shift to a neutral state; the probability of maintaining La Nina decreases to 10 - 20%.
From June - August 2026, ENSO is likely to maintain a neutral state but gradually lean towards the hot phase, with the probability of transitioning to El Nino increasing to about 35 - 45%.
From the beginning of autumn 2026, the hot tilt neutral state will be clearer and is likely to shift to El Nino in the last months of 2026, early 2027.
This phase transition development is expected to increase the uncertainty of extreme weather phenomena globally as well as regionally.
With ENSO developments like this, what is the forecast for the hot sun trend in 2026, sir?
- In the context of global temperatures still maintaining at record highs, according to the World Meteorological Organization's warning, 2026 is likely to continue to be in the group of hottest years since the observation data was available.
When ENSO leans towards the hot phase from the second half of the year, monsoon winds in the Pacific Ocean tend to weaken, convection distribution changes, increasing the probability of prolonged and more extreme heat waves appearing in tropical areas, including Vietnam.
At the same time, rain in some Southeast Asian regions, especially in the south of our country at the end of the year, may be lower than the multi-year average.
Sir, what is the forecast for the starting time of hot spells for each region?
- For Vietnam, in the context of ENSO phase transition and hot tilt as well as the impact of climate change, hot weather in 2026 is forecast to appear early, last longer and increase in intensity compared to the multi-year average, even more intense than in 2025.
In March 2026, hot weather will continue to occur widely in the Southeast region; the Northwest region may experience localized hot weather. In April 2026, hot weather will increase in intensity and expand to the Central Highlands and the Southwest region; hot weather waves begin to appear in the area from Thanh Hoa to Hue.
From the end of May 2026, hot weather will gradually expand to the entire Northern and Central regions, intensity will increase sharply and maintain peak periods in June - August 2026.
From around September 2026, the heat will tend to gradually decrease but there may still be unusually late heat waves.
Overall, extreme heat is no longer a strange phenomenon but is becoming an increasingly clear characteristic in the context of climate change and ENSO shifting to a hot phase.
Thank you very much, sir!
