The Met Office has now issued an amber warning for London and the south east, up from a yellow one put out earlier in the week, meaning there is an increased likelihood of bad weather affecting the area.
Laura Patterson, Chief Operational Meteorologist at the Met Office, said: "A cold easterly airflow is expected to return during the weekend, likely lasting until Monday".
But now the yellow warning has been extended until 10am on Monday, with ice on roads, pavements and cycle paths likely either where melted snow refreezes or where further wintry showers occur causing unsafe travel conditions, mainly in the east of England and Scotland.
There is a chance that power cuts will happen, and some rural communities could be cut off.
"Some injuries are also possible from slips and falls on icy surfaces".
St Patrick's Day parades could be hit with a two-inch blanket of snow as another cold snap takes grip, experts have warned.
The Met Office warnings for snow and ice begin at 6pm on Friday for eastern Scotland and England, and run into all of Saturday, where nearly the entire country is included.More news: Labour leader Jeremy Corbyn in Cumbria
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The cold weather is only expected to last a few days - by Tuesday temperatures will be getting back to average for the time of year.
The Met Office warnings for snow and ice begin at 3pm on Friday for central and eastern Scotland and the north east, and run into all of Saturday where more of England is included.
Snow will initially affect northeastern Scotland and northeastern England, before spreading to the rest of the UK.
Public Health England have issued a Level 3 Cold weather alert for the coming weekend. Especially on the eastern side of Ireland, 1C to 2C with a significant wind-chill factor.
A yellow warning for snow and ice is in force for most of Shropshire from just after 00.05am on Saturday morning through until 11.55pm.
The Met Office said: "Snow showers are likely to continue throughout Sunday, and where these converge some snow may well accumulate and could then prove disruptive".