The northern region has experienced several days of strong heat at the end of September, with temperatures in many midland and delta areas reaching 35–36°C and exceeding 36°C in some locations.

On September 29, temperatures reached 36.8°C at Lang station in Hanoi, 36.6°C in Kim Boi and 36.3°C in Nho Quan (Ninh Binh province). Relative humidity fell to around 45–55%, adding to the hot and dry conditions.

The heat is forecast to continue on September 30. According to the National Centre for Hydro-Meteorological Forecasting, Hanoi could see highs of 35–37°C, while temperatures in the northeastern and northwestern regions are expected to reach 33–36°C, with some areas exceeding 36°C. The southern part of Phu Tho province could also reach 35–37°C.

Why is northern Vietnam still so hot in late September?

The current heat is linked primarily to the prevailing atmospheric pattern. Nguyen Hong Sinh, deputy director of the Hai Phong Hydro-Meteorological Station, said the southern edge of a low-pressure trough is influencing the lower atmosphere.

A warm and humid air mass at higher levels is also contributing to higher temperatures. The combination of prolonged sunshine, limited cloud cover and little rainfall has created favourable conditions for daytime heating.

The occurrence of temperatures above 35°C in late September may feel unusual after northern Vietnam has begun transitioning towards cooler autumn weather. However, such late-season hot spells can still occur during the seasonal transition and do not necessarily represent an unprecedented weather event.

Late-season heat remains possible in 2026

The current spell also comes against a broader backdrop of relatively high temperatures in 2026.

Nguyen Van Huong, head of the Weather Forecasting Department at the National Centre for Hydro-Meteorological Forecasting, previously said that changes in ENSO, together with the influence of climate change, could contribute to more intense or prolonged heat episodes during the year.

The national weather service had forecast that heat would gradually ease from around September, but late-season hot spells could still occur. The current episode therefore fits within the range of weather conditions previously identified for the transition period, even though its timing makes it feel unusual to residents.

At the same time, the current heat should not be attributed solely to climate change. The immediate cause is the specific atmospheric circulation pattern affecting northern Vietnam, while climate change is a broader factor that can influence the frequency and intensity of extreme heat over longer periods.

Cold air to bring an end to the heat

The hot spell is expected to be short-lived. A weak cold-air mass will begin affecting northern Vietnam from the night of September 30, bringing scattered showers and thunderstorms and a drop in temperatures on October 1–2.

The weather is expected to change more noticeably from around October 4–5, when the cold air could strengthen. Rain is forecast to increase across northern Vietnam and from Thanh Hoa to Ha Tinh, with locally heavy rain possible.

The transition from intense heat to rain and cooler weather within a few days is characteristic of the seasonal change, when shifts in atmospheric circulation can produce marked fluctuations in temperature.

For northern Vietnam, the first days of October are therefore expected to bring a more typical autumn pattern, with lower temperatures, increased rainfall and occasional thunderstorms.

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