Sizzle puzzle: how Vietnam’s hottest locations came to be

Nghe An’s Tuong Duong, Ha Tinh’s Huong Khue and Quang Tri’s Dong Ha districts have been the hottest locations for the last few years. Towards the end of June and in early July, the mercury climbed to at least 35 degrees Celsius for weeks in these districts.

These days, as early as 9 a.m., the asphalt in Dong Ha is a hot pan on which the proverbial egg can be fried. People are generally quickening their pace to get away from the streets to some form of shade.

In Tuong Duong and Huong Khue, crops have withered in many fields and the districts are dotted with parched land patches and barren lakes.

Nguyen Van Huong, head of the climate forecast department with the National Center for Hydro-Meteorological Forecasting, said Tuong Duong, Huong Khe and Dong Ha are currently the three hottest locations in Vietnam, with temperatures 0.5-2 degrees higher than other localities.

On April 20, 2019, Huong Khe had seen a record-breaking temperature of 43.3 degrees, the highest ever recorded in a Vietnam locality. The Washington Post said the temperature was “the latest in a mounting list of records to fall as the world continues to warm,”, adding that it was hot enough to “soften your crayons, liquefy chocolate and raise the temperature inside a parked car past 140 degrees Fahrenheit (60 degrees Celsius).”

Huong said the hottest locations were all located in the western mountainous region of central Vietnam, which are most affected by a hot, low-pressure area in the west, as well as the effects of Foehn winds. These two factors contributed to all the harsh heat waves in central Vietnam, he added.

The Foehn winds originate from the Gulf of Thailand and move over Cambodia and Laos to the southwest-northeast. When it reaches the Annamite Range, it speeds up and rushes towards northern and central Vietnam regions. The winds typically show up between April and September, blowing from morning til dusk, and is at its strongest at noon and the afternoon.

“The wind is dry and hot, making the climate harsh. Moisture drops to 30 percent and temperatures go up to 43 degrees,” Huong said.

Tang Van An, head of the forecasting department of the North Central Regional Hydro-Meteorological Center, said years with the El Nino phenomenon often see higher temperatures than years without. Geographical features may also play a role, he said. For example Tuong Duong has many limestone mountains, which reflect radiation and thus cause higher temperatures. The lack of trees in Huong Khe also drives the heat up, he added.

Besides high temperatures, these locations also experience a high number of hot days. The North Central Regional Hydro-Meteorological Center said that a year in northern-central Vietnam sees around 50-100 hot days. Hot days would begin in April and peak in June or July.

Among the three locations, Dong Ha has the highest number of hot days. There were around 112 hot days in 1992, and the average number per year was 71 since 1990.

Long heat waves kill crops, dry out riverbeds and facilitate salt intrusion. But some experts say that hot climate can also be advantageous for certain crops, and that the extra sunlight received can be used for power generation and other purposes.