BEIJING -- China's national observatory upgraded its snowstorm warning to the second highest level Thursday, as heavy snow continues to hit areas in central and eastern China.

The National Meteorological Center (NMC) issued an orange alert for Thursday and Friday, as 10 to 20 centimeters of snow was expected in parts of Anhui, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shanghai and Zhejiang.

Blizzards in some areas are expected to last more than three days, with new snow falling up to 20 centimeters, it said.

The center advised residents to stay indoors and urged local authorities to take precautions on roads, railways, electricity and telecommunications.

The observatory maintained a blue alert for a cold wave Thursday, as temperatures in central and eastern China continue to decline due to the cold front.

In the country's four-tier weather warning system, red is most severe, followed by orange, yellow and blue.