An icy cold spell, the season's first, has hit northern Vietnam, hospitalising thousands of children and creating fog-related traffic jams.
Day temperatures are no higher than 7-10 degrees Celsius - and ice has appeared on the top of Mau Son mountain in Lang Son Province's Loc Binh District. Temperatures dropped to minus 0.8 degrees. The temperature in Sapa in Lao Cai Province fell to a chilly 2.7 degrees.
The cold spell has been accompanied by thick fog, which has caused traffic blockages in some areas.
The mountain region is expected to experience slightly warmer weather during the weekend with temperatures about 13-14 degrees, said Le Thanh Hai, deputy director of the National Hydro-meteorological Forecast Centre.
However, he warned that between four to five colder spells were likely to hit the region between mid-December and the end of February.
The cold weather has led to sickness in many children, including respiratory disorders, bronchitis and pneumonia.
The Hanoi-based National Hospital of Paediatrics reported it had received 1,500-2,000 children a day recently, nearly double normal attendances.
Deputy head of the hospital's Respiratory Diseases Department, Le Hong Hanh, warned parents not to let their children play outside.
The Hanoi Department of Education and Training has ordered education and training offices in the city to take measures to ensure the health of pupils.
Deputy director of the department Doan Hai Vinh said heads of schools, particularly those in remote and difficult areas, had been told to check facilities to ensure classes have proper windows and doors as well as lighting systems.
They were also instructed to adjust school times so children were not compelled to attend so early on freezing or wet days.