The La Nina phenomenon - the "cold version" of El Nino - has officially returned to the Pacific Ocean, marking a period of global fluctuations.
According to the US Environment and Ocean Administration (NOAA), La Nina is not a rare phenomenon, but each time it returns, it leaves a different impression. Winter 2025 is predicted to be a period of strong La Nina domination, although only a weak and short-term phenomenon.
AccuWeather hurricane forecaster Alex DaSilva said that La Nina often makes the end of the Atlantic hurricane season more dynamic.
The reason is that when La Nina appears, the phenomenon of high-level wind shear - a factor that can "squeeze" tornadoes - will decrease significantly, helping storms form easily and maintain strength for longer.
As of the end of October, the Atlantic has recorded 13 named storms, including four that reached super typhoon status. There are an average of 14 typhoons per season, seven of which become strong.
According to NOAA, La Nina years typically have twice as many storms in November as neutral years or El Nino years, due to more favorable atmospheric conditions. This means that the 2025 hurricane season may not end on schedule on November 30, especially in the Caribbean and Southeast regions of the United States.
La Nina also clearly shapes the winter weather pattern in the Northern Hemisphere. According to the US Climate Prediction Center (CPC), the Northwest will be colder and foggier, while the South and the Midwest will be dry and less rainy.
Jon Gottschalck, CPC's weather forecast chief, said that while La Nina 2025 is considered weak, its impact will be strongest in the winter, when the atmospheric system in the Northern Hemisphere becomes more sensitive.
La Nina itself is just a phenomenon of colder-than-normal ocean waters, but the consequences it brings can be serious.
In the past, La Nina has been associated with heavy rains causing flooding in Southeast Asia, droughts in South America, forest fires in Australia, and major fluctuations in global agricultural productivity.
According to the Vietnam National Center for Hydro-Meteorological Forecasting, La Nina often causes the North of Vietnam to be colder than the average of many years, while the Central and Central Highlands regions will have more rain at the end of the year.
If this phenomenon continues into early 2026, the Central region may experience 1-2 more heavy rains late, while the South will enter the dry season earlier but still have unseasonal rain.
Experts also warn that, in the context of global climate change, the ENSO ( El Nino - La Nina) cycle is increasingly fluctuating erratically, making long-term forecasting more difficult.
