The severity of this anomaly was quantified in the temperature records set during the first 48 hours of October. A total of 42 temperature records were broken across the North. The peak of this thermal spike occurred in the Lang area of Hanoi, where the thermometer climbed to 38.4 degrees Celsius. This figure not only represented the highest temperature of the heatwave but also established a new historical high for October at that specific weather station. Such deviations from the baseline climate pattern illustrate a broader shift in the regional meteorological profile, where extreme events are becoming more frequent and intense.
Scientists attribute this unusually hot autumn to a convergence of global and regional atmospheric factors. Mr. Nguyen Duc Hoa, Deputy Head of the Climate Forecasting Department at the National Center for Meteorological and Hydrological Forecasting, explained that the primary drivers include the long-term trend of global warming, which raises the baseline risk of intense heatwaves, and the occurrence of a strong El Niño event. Statistical analysis indicates that in years with very strong El Niño conditions, average monthly air temperatures from the previous autumn through the following summer tend to exceed multi-year averages by one to two degrees. Furthermore, the specific heatwave in late September was exacerbated by the southern edge of a low-pressure trough, with its axis positioned at approximately 25–28 degrees North latitude, which was compressed by a continental high-pressure system. This dynamic trapped warm air over the northern delta and coastal areas, sustaining high temperatures even into late October.
As the intense heat began to wane, the atmospheric conditions in the North shifted, leading to a rapid transition in weather patterns. By October 25, the same region that had endured extreme highs was experiencing cloudy skies, cold weather, and scattered rain. The meteorological forecast for this date highlighted a stark contrast: while Central and Southern Vietnam faced moderate to very heavy rain and thunderstorms, the North saw temperatures drop significantly. In the Northwest region, some areas recorded freezing temperatures, while mountainous zones in the Northeast saw lows below 17 degrees Celsius. In Hanoi, northeasterly winds at force 2–3 accompanied a drop in temperature, with the lowest reading between 19 and 21 degrees Celsius and a high of only 22 to 24 degrees Celsius.
This cooling trend is driven by a strengthening cold air mass that began impacting the northeastern region, Thanh Hóa Province, and parts of the Northwest on Monday morning. By 7 a.m., this mass had already pushed temperatures in these areas down to 21–24 degrees Celsius. The cold front is forecast to spread further, affecting areas from Nghệ An to Huế later in the week. The National Centre for Hydro-Meteorological Forecasting warned that the minimum temperatures during this cold spell would range from 18 to 21 degrees Celsius across the northern plains and Thanh Hóa, but would fall to 14 to 17 degrees Celsius in high mountainous areas. For Hanoi residents, the lowest temperature on Monday was forecast to be 22 degrees Celsius, a sharp decline from the 38-degree highs recorded just weeks prior.
The arrival of the cold front is not merely a drop in temperature but is accompanied by significant precipitation and wind risks. Strong northeasterly winds of force 6, occasionally reaching force 7 with gusts up to force 8, are expected in the Gulf of Tonkin, generating waves of 2 to 3 meters and creating rough sea conditions. These maritime hazards pose risks to vessels and disrupt local transport activities. On land, the interaction between the cold front and an upper-level easterly wind disturbance is triggering widespread heavy rainfall, particularly in Central Vietnam. From the evening of October 27 to the end of October 29, the strip from Hà Tĩnh to Đà Nẵng is under influence of these combined forces, with total rainfall generally ranging from 60 to 120 millimeters, and localized areas receiving over 250 millimeters.
The intensity of this rainfall has been recorded in specific bursts, with some areas in the central region receiving over 100 millimeters of rain in just three hours. The meteorological agency has issued warnings that such heavy rain, combined with the potential for thunderstorms, lightning, and hail, could trigger flash floods in small rivers, landslides on steep slopes, and flooding in low-lying areas. These hydrological risks are compounded by the strong wind gusts, which can damage crops, trees, and housing infrastructure. The juxtaposition of the recent record-breaking heat and the current cold, wet spell highlights the increasing volatility of the regional climate, where extreme thermal and hydrological events are occurring in rapid succession.
Looking ahead to early November, forecasts indicate that the cold front may strengthen further. Mr. Hoa predicted that from November 1 to 2, the North will experience a more pronounced drop in temperature, with cool weather at night and in the morning in the lowlands and potentially cold conditions in the mountainous provinces. This transition signals the definitive end of the anomalous hot October and the establishment of winter weather patterns. For communities in the highlands, the drop to below 17 degrees Celsius and the potential for freezing temperatures in localized areas will require immediate adaptation measures for agriculture and daily life. The cycle of extreme heat followed by sharp cooling and heavy rain underscores the need for continuous monitoring, as the underlying drivers of climate change and El Niño continue to modulate the intensity of these seasonal extremes.
