Beijing's warmest New Year's Day in decades saw people flood outdoors on Wednesday, the first day of 2014.

According to the Beijing meteorological bureau, the capital's temperature was 12.8 C at about 2 pm on Wednesday, the warmest since 1951.

There have only been five times since 1951 that Beijing's first winter snowfall took place in the new year.

The warm weather on New Year's Day drew tens of thousands of people in Beijing outdoors.

About 20,000 people gathered at Tian'anmen Square to attend the flag-raising ceremony at 7:36 am.

"It is such a treasured experience to witness the solemn ceremony," said Li Yinghao, a 10-year-old boy from Heze, Shandong province.

Li and his mother rushed to the ceremony at around 5 am, directly after a 9-hour train journey from their hometown.

Tang Zhenfu, a student at the China Institute of Industrial Relations, went to the flag-raising ceremony by bike, instead of riding the subway, which takes about 50 minutes. Tang said he was happy to embrace the first day of 2014 on a sunny, breezy and clear day.

Also on Wednesday, a group of 2,014 people climbed Badaling Great Wall to mark the New Year. Parks in Beijing were crowded with thousands of people, many with their elderly parents and children.

Sun Jisong, chief forecaster of the Beijing meteorological bureau, said that the temperature at New Year in Beijing was about 8 degrees higher than the average of the past three decades.

In the coming week, the capital is unlikely to welcome its first snow, he said.

"Although Beijing experienced a warmer New Year, it is still early to say that this winter will be warmer than usual," Sun said.

Experts, however, warned people of the danger of getting sick as such warm weather results in dry air.

It is more likely people will catch cold or flu viruses in dry air, as many viruses that cause respiratory problems can float around more easily, said Wang Guangfa, director of the respiratory medicine department of Peking University First Hospital.

However, he said he hasn't seen an obvious increase of patients having respiratory problems.

Beijing's flu season is from December to January, but neither the number of flu-like symptoms nor the proportion of flu among cases tested in December is higher than last year, said Pang Xinghuo, deputy director of the city's center for disease control and prevention.

Outside Beijing, most of the country was experiencing a warm New Year.

In Hangzhou, Zhejiang province, the temperature reached a record high of 16 C, and in Hefei, Anhui province, the mercury rose to 17 C, breaking the previous high on Jan 1 by 9 degrees, according to the China Meteorological Administration.