About 500,000 people - most migrant workers - were stuck in the southern city of Guangzhou, railway officials said. Heavy snowfall in provinces to the north had cut off parts of the busy railway line that starts in the city and ends in Beijing.
The crash brought the known death toll in the last two weeks to about 50. Xinhua News Agency said the bus veered off the road - covered by a thick layer of ice and snow - in mountainous Guizhou province at 7:40 a.m.
The new agency said that in addition to the 25 deaths there were also 13 people injured, accounting for all 38 aboard. Two passengers were hospitalized in critical condition, while injuries to the 11 others were less serious.
The government, scrambling Monday to prevent riots among the crowds that have swelled daily since the storms began Jan. 10, offered temporary shelter in schools and convention centers. Hundreds of police and soldiers were posted around the train station.
Frustrated in their efforts to return home, migrant travelers created small camps of suitcases in the mud outside the train station, scattering chicken bones and cigarette butts.
Li Moming, a construction worker among those stuck in Guangzhou, wore a mud-splattered pinstriped suit for a homecoming that might not happen. He spent the night on the street in a cold drizzle. The train to his village in central Henan province, 20 hours away, was canceled. He might have to spend the holiday at his work site instead.
"What can you do?" he said. "It's the weather. It's nobody's fault. You can't control the weather."
Chinese New Year begins Feb. 7 - when the train station will start to sell tickets again, radio reports said. State-run newspapers ran headlines urging the migrants not to travel. But for many migrants, the New Year - China's most festive holiday - is the only chance for months to visit their families, and they stay away for weeks.
One young mother who would give only her surname, Yang, spent the night on the street in front of the station with her 7-month-old daughter. She said she would probably have to cancel her holiday visit with her family and return to her small apartment near her factory.
Many workers were stoic, accustomed to the huge crowds, discomforts and long delays that are common for China's poor. But others fought among themselves while trying to board long-delayed trains during the busiest travel season of the year.
The great effort put into managing the Guangzhou crowd did not surprise Susan Shirk, whose recent book, "China: Fragile Superpower," discusses how domestic unrest poses a serious threat to the communist regime.
"When large numbers of people are upset about the same problem at the same time, there is a risk of large-scale collective action that could threaten Communist Party rule," said Shirk. "Will the travelers blame the weather or the government?"
A new round of blizzards threatened central Chinese provinces Monday, putting more pressure on already strained transport, communications and power grids. The weather has already affected 67 million people.
The storms, which have killed 24 people since they began, have already caused economic losses of $2.5 billion, the Civil Affairs Ministry said. The storms snapped power lines for trains in neighboring Hunan province - a midpoint for the busy rail line that runs from Guangzhou to Beijing.
The government pledged Monday to increase the output of gasoline, coal and power to ease shortages amid the severe winter weather, which has forced rationing in some areas, the Xinhua News Agency said.
The announcement came as coal prices hit a record high Monday and heavy snows blocked deliveries to power plants. The government was already struggling to ease shortages of pork, grain and other food items that have set off a sharp rise in inflation.
On Friday, the Cabinet ordered local authorities to ensure adequate food supplies to keep prices stable ahead of the New Year.
