Storm Arwen, a low-pressure system across the country, is set to bring strong winds, with gusts of up to 60mph in places, heavy rain, and even sleet and snow to some parts.
The strongest winds will arrive across northern Scotland during Friday afternoon and will then spread across the rest of Scotland, Northern Ireland, and some exposed coasts of northern England by evening, and the rest of the UK, bar the far south east of England, on Saturday.
Chris Almond, Met Office deputy chief meteorologist, said: “As well as strong winds, rain will also move south across the country on Friday, with showers following turning increasingly to hill snow in the north.
“This wintry mix of showers will continue on Saturday, and although snow is possible almost anywhere away from the far-south, accumulations are likely to be confined to hills.
“It is going to be a windy period with potentially disruptive gales.
"These could cause some delays to road, rail, air and ferry transport with a small chance exposed roads and bridges could close.
"There is a slight chance of some damage to buildings, such as tiles blown from roofs and damage to temporary structures such as Christmas markets.”
In a marked change from autumn so far temperatures will be widely below average for many with daytime temperatures in single figures for most with overnight frosts possible.
A council spokeswoman said: “As with any extreme weather conditions a decision will be made on the day as to the safety of the market and associated events going ahead.
“Our town centre team will take a view on this and we will communicate any changes on our social media feeds.”