BEIJING, Jan. 23 -- China's national observatory raised the weather warning level from yellow to orange on Saturday morning as much of the country braced for the worst cold in 30 years.

According to the National Meteorological Center (NMC), temperatures dropped 6 to 10 degrees Celsius on Saturday morning in parts of northwest China, north China and the Huanghuai area.

China has a four-tier warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.

In the worst-affected areas such as eastern Hebei Province, northern Shandong Province and eastern Qinghai Province, the cold front brought down temperatures by 11 to 16 degrees Celsius, the NMC said.

In Beijing, temperatures dropped to under minus 10 degrees Celsius on Friday and will hit a 30-year low of minus 16 degrees Celsius from Saturday through Sunday, the Beijing meteorological station said.

At 7:00 a.m. Beijing Time on Saturday, all regions north of the Yangtze River, except eastern Sichuan Province and Chongqing, saw temperatures drop to below zero degrees Celsius, according to the NMC.

The NMC also expected temperatures in South China and Southeast China to drop by 6 to 10 degrees Celsius from Saturday to Monday.

Temperatures in central and eastern regions of China were 6 to 8 degrees Celsius lower than the average historical level.

Temperatures in parts of Anhui, Zhejiang, Fujian and Guangdong are forecast to approach or even drop below the lowest levels on record, it said.

The NMC issued a yellow alert for the cold weather on Thursday.