A thick layer of haze shrouds high-rise buildings in Ho Chi Minh City on the morning of October 15, 2026. Photo: Le Phan / Tuoi Tre
Ho Chi Minh City woke up to unusually hazy skies on Thursday, with the murky conditions lingering into midday, a stark contrast to the clear skies and strong sunshine seen the previous day.
Meteorologist Le Thi Xuan Lan said the phenomenon was a combination of dry haze and fog, caused partly by weak southeasterly winds that allowed airborne dust and pollutants to accumulate near ground level.
She said transboundary haze from Indonesia, which has previously affected several Southeast Asian countries, including Singapore and Malaysia, could also reach southern Vietnam.
However, she stressed that measurements were needed to determine whether smoke from Indonesia had contributed to Thursday's haze.
"In the past, dust and transboundary haze from forest fires in Indonesia have spread to and affected southern Vietnam, including Ho Chi Minh City," Lan said.
Whether smoke, dust or haze is currently reaching southern Vietnam depends heavily on wind direction and atmospheric conditions.
"When winds have a southerly component, such as southwesterly or southeasterly winds, atmospheric conditions can carry air masses northward, potentially transporting smoke from Indonesia into southern Vietnam," she explained.
There was not yet sufficient evidence to confirm whether smoke from Indonesia was responsible for Thursday's conditions.
Meanwhile, Le Dinh Quyet, head of the forecasting department at the Southern Regional Hydrometeorological Center, said the hazy conditions were not unusual and could be explained by local weather patterns.
Rain overnight had left high moisture levels in the lower atmosphere, while weak winds and low clouds prevented the moisture from dispersing.
In densely built-up urban areas, high-rise buildings further restrict air circulation, allowing mist to linger near the ground and reduce visibility, he said.
Early-morning humidity in Ho Chi Minh City and southeastern Vietnam ranged from 91 to 96 percent, while low clouds covered around 60-80 percent of the sky.
The combination of high humidity, weak winds and limited sunshine allowed the haze to persist well into the day.
Quyet added that a weak low-pressure trough, a retreating subtropical high-pressure system and lingering easterly wind disturbances were contributing to the weather conditions across southern Vietnam.
Indonesian forest fires raise regional air pollution concerns
Indonesia is grappling with one of its worst forest fire seasons in years, with prolonged dry conditions, worsened by a strong El Niño, allowing land-clearing fires to spread out of control.
The fires, particularly on the islands of Sumatra and Borneo, have caused widespread damage and serious health concerns, with more than 283,000 respiratory illness cases reported in affected areas.
In Bangka Belitung Province, fires have destroyed nearly 300 homes and forced hundreds of residents to evacuate.
Smoke from the blazes has also drifted into neighboring countries, including Singapore and Malaysia, raising concerns over transboundary air pollution and public health.
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