ICY conditions with sub zero temperatures could hit North Wales for at least a week, the Met Office has said.

The forecaster extended Wednesday’s yellow weather warnings into Thursday and Friday.

Arctic air, dubbed the Troll of Trondheim, will quickly move south during Wednesday, leaving most of the country in its grip by Thursday morning.

The yellow ice warnings are in place for all six North Wales counties, the first starting at 5pm today and the third ending on Friday.

A Met Office spokesman said: "Frequent wintry showers are likely to fall on frozen surfaces in places, leading to the formation of icy patches. These showers are likely to fall as snow on high ground, with the potential for several centimetres to accumulate over parts of southern Scotland, Northeast England, North Wales, the North York Moors and Northern Ireland.

Temperatures will be below freezing at times in all parts of North Wales this week, with nighttime temperatures falling as low as -3C.

Met Office spokesman Grahame Madge said: “We are in this pattern for seven days at least.

“We could see it continue for a while longer, there’s uncertainty in the evolution and how long it will last.

“However, the pattern for the next seven days is that it will remain cold and we will see double digit minus figures overnight in areas that are prone to frosts and areas where there is lying snow.”

There was no expectation of widespread heavy snow, but wintry showers were expected during the cold spell, particularly on higher ground and by the coast, Mr Madge said.

Cold air from the north tended to contain less moisture than from the west, meaning less cloud cover and therefore lower overnight temperatures.

Mr Madge said although this will be a cold snap, it will not be as tough as the “hard December” of 2010.

Nationally, Age UK advised people to maintain a supply of food and medicine to reduce the number of outdoor trips and torches with spare batteries in case of a power cut.