A watch tower in the Mau Son Tourist Area in Loc Binh District, around 1,500 meters above sea level, was covered in a thick layer of frost on Monday morning as temperatures dropped to 1 degree below zero.
Snow and ice covered the ground and trees to a thickness of 5-6 cm.
A group of tourists inside the watch tower. Normally people can see the entire tourist area from there, but on Monday thick fog prevented visibility.
Mau Son, which used to be a favorite attraction for the French upper class and has dozens of French-built villas and old houses that are now abandoned, has become a growing tourist attraction in recent years, especially in winter.
Since February 18 a mass of cold air combined with rains has plunged northern Vietnam into its coldest spell this winter.
Hoang Lang Huy, a resident of Lang Son, said his family arrived on Mau Son on Saturday night after hearing the temperature would fall below zero. But all accommodation facilities were full, and his family had to stay at a local's house.
Huy's wife and two-year-old daughter in warm clothes next to a tree completely covered in ice.
He said: "Almost every year my family comes to Mount Mau Son to see frost. We have a lot of warm clothes and travel here by car to ensure we remain healthy."
Huy's nephew walks amid plants covered with frost.
"When the temperature fell below zero, there was fog and rain and it was cold. Every 20 minutes I have to warm my hands and dry the camera."
Tourists pose for photographs amid the icy landscape.
Nguyen Minh Chuyen of the Mau Son Tourism Promotion Information Center said some 8,000 people visited Mount Mau Son in the past three days, and hotels were all full. Many people had to sleep in their cars or return to the downtown area to find accommodation.