Late September and early October usually mark the transition between seasons in northern Vietnam. Weak cold air masses typically move south during this period, bringing thunderstorms, slightly lower temperatures and cooler conditions at night and in the early morning.
This year, however, the region experienced summer-like heat from September 28 to October 2. Temperatures measured in standard meteorological shelters exceeded 38 degrees Celsius in many places, while actual temperatures felt above 40 degrees, particularly in the inner districts of major cities such as Hanoi.
According to the National Centre for Hydro-Meteorological Forecasting, the unusual heatwave set 73 temperature records nationwide. Of these, 51 were recorded in the north, including 10 records for the highest September temperatures and 41 monitoring stations that registered their highest October temperatures.
Lang station in Hanoi recorded the highest temperature during the period, reaching 38.4 degrees Celsius on September 30. This set a new September temperature record for the capital, surpassing the previous record established in early September 2025.
Yen Chau in Son La Province recorded 38.3 degrees on October 3, exceeding its previous record set in 2019, another year marked by a very strong El Niño.
Besides Hanoi and Son La, temperature records were set across much of northern Vietnam, including Lao Cai, Lang Son, Cao Bang, Tuyen Quang, Dien Bien, Lai Chau, Phu Tho, Hung Yen, Ninh Binh and Haiphong. Only three localities, Bac Ninh, Thai Nguyen and Quang Ninh, did not register record temperatures.
Record heat was also reported at several monitoring stations in central and southern Vietnam during the same period, indicating that unusually high temperatures were affecting the country more broadly.
In the days that followed, northern Vietnam continued to experience relatively hot weather. A cold air mass arriving on the night of October 4 brought a slight drop in temperatures on October 5 and 6, but from October 7, daytime highs returned to around 33-34 degrees Celsius, accompanied by strong sunshine.
Forecasts for the 10 days from October 12 indicate that the north will remain unusually warm, with daytime highs of 32-34 degrees, mostly sunny conditions and little rain. No cold air mass is expected to arrive during this period.
The National Centre for Hydro-Meteorological Forecasting has also warned that, with a super El Niño emerging, northern Vietnam is likely to experience fewer cold air outbreaks than the long-term average this winter. These systems are also expected to be weaker, with fewer and shorter spells of severe and extreme cold.
As a result, the region is likely to face an unusually warm winter.
However, forecasters have not ruled out the possibility of powerful cold air outbreaks during the peak winter period, from the second half of December 2026 to February 2027. These could still produce record-low temperatures in northern Vietnam, underscoring the growing unpredictability and severity of extreme weather under changing climate conditions.
