Met Office forecasters have warned of an increased chance that temperatures will turn colder than average at the start of 2019, thanks to an atmospheric phenomenon known as Sudden Stratospheric Warming.
SSW is when the temperature suddenly rises high up into the atmosphere which sets off a chain reaction that leads to extremely cold weather from eastern Europe and Russia.
A Met Office spokesman previously explained the phenomenon on its website:
"Sudden stratospheric warming events occur high up in the atmosphere and involve a complete reversal of the high altitude polar jet stream – they can even affect weather at the surface, and for the UK a sudden stratospheric warming increases the risk of wintry weather.”
"The phenomenon begins with a wave-like disturbance which travels up into the high-altitude jet stream. This disturbance can grow to a point where it turns over and breaks, just like a wave on a beach.
"Normally the jet stream flows from west to east with some north and south oscillation, but the force from this high altitude disturbance pushes against the jet stream until the winds actually reverse and flow from east to west instead. Air then falls into the Arctic and is compressed so that it starts to warm: the temperature can rise by as much as 50C in just a few days.
“This reversal of high altitude winds can also burrow down into the lower stratosphere. Once it is within reach of weather systems in the lower atmosphere the Atlantic jet stream often weakens and moves south. This allows cold air from the east into northern Europe and the UK.”
In 2018 Leeds, Hull, Sheffield and various parts of Yorkshire were battered by the Beast from the East, which brought several inches of snow on more than one occasion, closing schools, disrupting travel and leading to chaos out on the roads.
If the Beast from the East does return for 2019, we could be in line for similar scenes again.
It isn't clear exactly when Sudden Stratospheric Warming could cause snow to hit the UK.
The first snow hit Yorkshire this winter in October, although it wasn't enough to settle anywhere other than the highest parts of Yorkshire.
Currently, the forecast for Leeds and much of Yorkshire for New Year's Day is pretty mild:
Generally cloudy with intermittent rain or drizzle over the Pennines but largely dry elsewhere. Cloud and rain clearing south early afternoon, with a few sunny spells developing to the north. Mainly light winds. Maximum temperature 10 °C.
Some mainly clear skies at first, leading to fog patches developing. Becoming breezy and cloudy later in the night, with outbreaks of drizzle and rain spreading over the Pennines. Minimum temperature 2 °C.
Outbreaks of rain clearing south to become dry and bright but windy for a time. Winds easing during the afternoon. A cold evening, with clear spells likely. Maximum temperature 11 °C.
Outlook for Sunday to Tuesday:
Breezy with patchy rain on Sunday and Monday, especially over the Pennines, but brighter in the east. Winds slowly moderating, with brighter conditions likely on Tuesday. Mild.