Snow, icy rain and fog caused flight delays and highway closures in many parts of China on Feb 24, the last day of the weeklong Lunar New Year celebration, when millions of travelers head back to school or work.

The return travel spree is even heavier than the preholiday migration, known as chunyun.

Beginning 14 days ahead of Lunar New Year, or Spring Festival, millions of people head home to reunite with family in the Chinese tradition. It is thought to be the world’s largest human migration, as 2.8 billion trips are expected during the 40-day travel period ending March 16.

The Central Meteorological Station forecast snow for most northern regions and rainy and foggy weather in most of the south.

Nationwide, the travel load of people on return trips to China’s cities was expected to peak between Feb 24 and Feb 27.

Beijing South Railway Station, the largest of four terminals in the capital, was expected to see 110,000 arrivals on Feb 24 and 130,000 on Feb 25, up from the 100,000 recorded on Feb 23. Highways feeding the capital were also heavily congested on Feb 24 as people rushed to take advantage of toll-free hours, which expired at midnight on Feb 24.