Child care services are in huge demand in Hanoi as kindergartens and primary schools close because the temperature has dropped below the safety measure of 10C in the big chill that has swept down from Siberia and China and engulfed half of Vietnam.

Hanoi schools close in big chill 

Pupils in secondary schools are unaffected unless the mean temperature falls below 7C, but young children must go home when it falls under 10C.

But with many families having both parents working to make a living, it is not easy for one to take time off with every change of the weather, and the burden falls on grandparents, other relatives, neighbours, or daycare centres, which costs VND200,000-300,000 a child.

Freezing temperatures were reported across the northern regions -- minus 0.4C in Tam Dao (Phu Tho Province), minus 0.2C in Dong Van (Ha Giang Province) and minus 4C in Mau Son Mountain (Lang Son Province).

In Hanoi, the temperature dropped below 5C, with snow reported at Ba Vi District, about 50km from the capital.

The cold snap is expected to last until at least January 27, although long-range international forecasts indicate further extreme cold weather ahead, especially during Tet, as temperatures drop to 60-year lows in China and Hong Kong.