ZHENGZHOU, Jan. 4 (Xinhua) -- The first snow of the New Year started hitting large parts of central China's Henan Province Wednesday, the local meteorological station said Thursday.

On Thursday morning, snow on the roads of Zhengzhou, capital of Henan, had reached 5 cm. Cars lowered their speed while environmental workers began cleaning snow off the roads.

The province banned seven-seater and above vehicles on expressways from 7 a.m. Thursday, while some primary and middle schools in Xinyang City suspended classes Thursday and Friday.

Meteorological experts said the snow could help increase humidity while improving air quality.

China's national observatory Wednesday continued a yellow alert for snowstorms in the central regions Wednesday and Thursday.

Parts of Shanxi, Shaanxi, Henan, Hubei and Anhui provinces should expect heavy snowfall during the period, resulting in up to 20 mm of snow in some areas, according to the National Meteorological Center.

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