Agencies explain increasingly frequent heavy rain in Ho Chi Minh City

From the beginning of 2026 through early October, nine days of rainfall exceeding 50 mm were recorded at Nha Be station and eight at Tan Son Hoa station, according to the Southern Regional Hydro-Meteorological Center.

By comparison, at Tan Son Hoa station, the average annual number of days with rainfall exceeding 50 mm was seven during 1990-2020 and 12 during 2021-25.

On September 21, rainfall at Nha Be reached 258 mm, the center said.

The Department of Agriculture and Environment said rainfall had increased over the past three years, with prolonged rainy spells and downpours exceeding 100 mm becoming more frequent.

Despite strong El Nino conditions, which are generally associated with less rain in southern Vietnam, Ho Chi Minh City experienced numerous days of heavy rain in September and early October 2026, the department said.

High tides have also become more frequent.

At Phu An station, water levels exceeded the second flood warning level of 1.50 meters 220 times from 2022 through September 2026, up from 151 times during 2017-21.

Water levels exceeded the third warning level of 1.60 meters 74 times in the more recent period, compared with 55 times earlier.

In November 2025, water levels reached record highs of 1.78 meters at Phu An station and 1.88 meters at Thu Dau Mot station.

The department attributed the city's flooding vulnerability to its low-lying terrain, climate change, rising sea levels and urbanization.

Expanding concrete and asphalt surfaces reduces rainwater absorption, while filling low-lying areas that naturally store water and allowing waste and sediment to accumulate in canals can further impede drainage.

At a press briefing on Thursday, a representative of the Ho Chi Minh City Department of Construction said the drainage system was designed to handle 85.3mm of rainfall over three hours and tides of up to 1.32 meters.

However, on September 30 and October 1, several monitoring stations recorded more than 100mm of rain in just 45 minutes to one hour, while tidal levels reached 1.42-1.56 meters.

Ongoing construction, aging or poorly coordinated drainage pipes, urbanization and land subsidence have further limited drainage capacity, the representative said.

Some areas have also experienced deeper flooding and slower water recession than in previous years.

To address flooding, the agriculture and environment department submitted a proposal to the Ho Chi Minh City administration on September 30 seeking funding from the Natural Disaster Prevention and Control Fund for urgent repairs, remedial work or construction at 134 disaster-prevention facilities across 23 wards and communes.

The city had previously approved urgent work at 89 critical facilities, which are expected to protect about 9,114 hectares of land and 10,144 households once completed.

Other measures include improving forecasts and warnings, repairing embankments, dredging and widening canals, upgrading drainage networks, tidal-control gates, pumping stations and regulating reservoirs, and coordinating the operation of Dau Tieng and Tri An reservoirs to reduce downstream flooding risks.