Unusual rains over 2 months cause devastating floods in northern Vietnam

Since June, which was the peak of summer in the north and before the peak rainy and flood season, the region has experienced 12 days of widespread heavy rains in two periods: June 4-10 and June 23-27. Rains were concentrated in the northeastern provinces, and the northern delta, home to Hanoi.

The National Center for Hydro-Meteorological Forecasting reported that the total rainfall in June in the north ranged from 200-600 mm, which is 40-80% higher than the average from previous years, and in some places along the northern coast, it was over 100% higher.

Earlier in the monthly forecast, the meteorological agency estimated that the total rainfall in the north would be only 10-30% higher than the multi-year average.

June set 13 records for daily rainfall and total monthly rainfall. The highest daily rainfall was recorded at 333 mm on June 9 in Quang Ninh Province, home to Ha Long Bay, surpassing the nation’s 2001 record by about 84 mm.

A 50-year record of 180 mm on June 24 in Hoa Binh Province was surpassed with a new mark of 195 mm. In Quang Ninh, the total June rainfall reached 1,100 mm, breaking its 1991 record by more than 120 mm.

For July, the National Center for Hydro-Meteorological Forecasting forecasted that the total rainfall across the country would be close to the multi-year average for the same period.

However, its rainfall exceeded forecasts, with periods of heavy downpours recorded on July 2-3 and July 15-19 in the northern delta, and then on July 23-24 and July 29-31 across the north, continuing into early August.

In July, the northwest received 350-500 mm of rainfall, with some places exceeding 600 mm; the northeast 250-500 mm, some places over 600 mm; and the northern delta 350-600 mm, 30-60% higher than the multi-year average.

Hoai Duc District in Hanoi received 685 mm of rainfall in July, 148% higher than the multi-year average; while Phu Ly Town of Ha Nam Province that borders Hanoi received 638 mm, 20% higher.

July set 12 records for monthly and daily rainfall.

Bai Chay Town in Quang Ninh received 950 mm in July, surpassing the 2015 record by about 50 mm. In Son La Province, two 30-year monthly rainfall records were broken: Son La City received nearly 600 mm, surpassing the 1994 record by about 77 mm; Co Noi received 577 mm, surpassing the previous record by nearly 140 mm.

The abundant rain kept the average temperatures in June and July lower than the five-year average.

The average June temperature at Lang Station in Hanoi from 2019-2023 was above 31 degrees Celsius, but this year it was 31 degrees. July’s temperature this year reached 30.5 degrees Celsius.

Nguyen Van Huong, Director of Weather Forecasting at the national forecasting center, explained that the heavy rains in June were due to a stronger-than-average monsoon trough in the north, which maintained a band of convective clouds in the area.

In July, heavy downpours were caused by the influence of a tropical convergence zone that extended across the north and central regions, connecting with a tropical depression over the East Sea. The rainfall on July 23-25 was influenced by the circulation of Storm Prapiroon, while the ongoing downpours are due to a low-pressure trough extending through the north, connected with a low vortex located over the north, developing from the ground up to 5,000 meters, Huong said.

Going into August, signs of La Nina are becoming clearer, and the complexity of rain and floods is expected to increase, meteorologists have said.