( CNN ) -- The recent snowstorm in China , which has stranded hundreds of thousands of people across the country and killed dozens , is related to the La Nina phenomenon , according to a Chinese weather expert . Suzhou , China , is blanketed by the most snow the city has had in 25 years , according to I-Reporter Susan Arthur . La Nina is the opposite of El Nino , which follows El Nino and occurs every few years . During La Nina , sea temperatures over eastern equatorial Pacific are lower than normal . La Nina enhances Arctic weather systems and causes a cold winter in Asia , including in China . As warm and moisture air from the south meets cold air in the north under freezing temperatures , snow forms . `` The warm air is very active this year , '' said Li Weijing , deputy director-general of the National Climate Center of China . As a result , persistent snowstorms occur in central and western China , paralyzing the transport and electricity systems . The current storm , which hit just ahead of the Lunar New Year holiday -- China 's busiest shopping season -- has shut much of the nation down . China 's transportation system and power grid have been paralyzed this week . The storm also has cost the nation 's economy $ 4.5 billion , according to figures released Wednesday by the Civil Affairs Ministry . Watch how Nanjing is coping with the unusual weather » . The winter precipitation had caused at least 49 deaths due to collapsed roofs and treacherous travel conditions , the Ministry of Civil Affairs and local officials said . More than 177 million Chinese were expected to travel by train , and 22 million more by plane , for the February 7 Chinese Lunar New Year , also known as the Spring Festival . China uses a color system for its snowstorm warning : . The current once-in-50-years snowstorm calls for the red warning , the first time such a warning has been issued since the system launches . E-mail to a friend . CNN 's Clarence Fong contributed to this report . Copyright 2008 CNN . All rights reserved.This material may not be published , broadcast , rewritten , or redistributed . Associated Press contributed to this report .
` ` The warm front is very active this morning '' , said Li . Current is responsible for the first - ever , most severe red warning . Hundreds of thousands of people have been injured , dozens dead .