The National Centre for Hydro-Meteorological Forecasting issued the warning at 7.30 am on October 9, highlighting the risk of flash floods, landslides and ground subsidence over the following six hours.
In the 24 hours to 7 am on October 9, moderate to heavy rain, with very heavy downpours in some areas, affected Hue, Danang and Quang Ngai.
Rainfall reached 279 mm in Thang Binh, Danang, 171.6 mm in Chau O, Quang Ngai, and 114.2 mm in Phong My, Hue.
Quang Tri also experienced heavy rain early on October 9, with Sen Thuy recording 107.8 mm and Dakrong 70.4 mm between 4 am and 7 am.
Forecasters said soil moisture had exceeded 85 per cent or reached saturation in several areas, significantly increasing the risk of flash floods and landslides if rainfall continued.
Over the six hours following the warning, Quang Tri was forecast to receive 20-40 mm of rain, with some areas exceeding 70 mm. Hue could see 10-20 mm, locally above 40 mm, while Danang and Quang Ngai were expected to receive 5-10 mm, with isolated totals exceeding 20 mm.
The weather agency warned that flash floods could occur along small rivers and streams, while landslides could affect hillsides and mountainous communities across the four localities.
In Quang Tri, areas at risk include Dakrong, Huong Hiep, Huong Phung, La Lay, Ta Rut, Cam Lo and Ba Long.
Warnings were also issued for parts of Hue, including A Luoi 1, Khe Tre, Nam Dong, Phu Loc and Chan May-Lang Co.
In Danang, vulnerable areas include Tra My, Tra Leng, Dong Giang, Tien Phuoc, Hiep Duc, Dai Loc and Hoa Vang.
Several areas of Quang Ngai, including Tra Bong, Son Ha, Son Linh, Son Thuy and Tay Tra, were also identified as being at risk.
The disaster risk level for flash floods, landslides and ground subsidence was assessed at level one.
Forecasters warned that flash floods and landslides could threaten lives, disrupt transport, damage homes and infrastructure, and affect agricultural production.
Local authorities were urged to inspect vulnerable areas and obstructed waterways and take preventive measures to minimise potential damage.
