China's annual Spring Festival travel rush began Wednesday.

China's annual Spring Festival travel rush began Wednesday in freezing weather, with some 700 million people, or half the nation's population, expected to travel within the country during the 40-day-long travel period.

China's Ministry of Transport (MOT) estimates that 2.85 billion passenger trips will be made during the period, 11.6 percent more than last year.

The Spring Festival, or Chinese Lunar New year, is the most important traditional festival of family reunions. This year, it falls on Feb. 3.

As usual, the peak travel season is pressuring China's transportation network, with passenger trips by railway up about 12.5 percent and those by plane up about 10.8 percent year on year, according to the country's transport authorities.

But freezing weather in south China is likely to disrupt travel and transportation, with temperatures down to their lowest since 1961 in the provinces of Guizhou, Hunan and Hubei.

A MOT report at 9 a.m. Wednesday said an expressway, seven national highways, and 36 provincial highways have been closed due to heavy snow and icy rain in the southwest municipality of Chongqing and the southern provinces of Guizhou, Sichuan, Yunnan, Anhui, Hunan and Hubei.