A rapidly developing area of low pressure will move east then south-east across the British Isles on Boxing Day. Rain will affect Ireland and south-western parts of England and Wales from early morning, spreading eastwards to affect all of Wales and much of the Midlands and southern England through the afternoon. South-westerly winds strengthening to gale force in the south-west. Eastern and north-eastern regions start chilly with a frost and early hazy sunshine, but becoming cloudy and remaining cool throughout the day. By late afternoon, rain will turn increasingly to snow for northern England, the north Midlands and the hills of Wales. Rain on and off for Northern Ireland. Most of Scotland remains dry but quite cloudy, hazy sun in the north-east and a few showers in the west. Temperatures 4 or 5C for the east and north, rising to 8 or 9C in the far south-west.
Boxing Day night
A large amount of uncertainty in precise details but as rain increasingly encounters colder air from about the Midlands northwards, there is the risk of turning widely to snow, even to low levels during Boxing Day evening and overnight into Saturday. Areas at greatest risk are North Wales, the southern Pennines, including Derbyshire and perhaps into the northern Midlands too. 2 to 4cm possible at low levels, but 10cm over higher ground. South from the Midlands, it is more likely to remain as rain, but as skies clear later, widespread ice will be a hazard. Scotland avoids the main area of precipitation, although snow showers may affect the north and west. Overnight temperatures around 2C in the south, to 0C in the Midlands and -2C in Scotland and northern England.
Low pressure moves south-east into the Low Countries during Saturday. Gale force winds around toward the south-east at first. A complex cluster of showers or longer periods of rain, sleet and snow moving southwards. Frequent snow showers for Wales, and also western regions of England including Devon and Cornwall, although mostly rain at low levels here. Belts of snow also threaten eastern counties of England and Scotland, falling to low levels, and may become more extensive for the eastern Midlands by evening, although uncertainty about the details. Central and western Scotland often dry, but heavy snow or hail showers near west coast, may also affect northern parts of Ireland, fewer showers further south. Temperatures 1 to 3C for most, nearer 5 or 6C in the south-west.
High pressure builds across the British Isles, giving a very cold and frosty start, with icy stretches after previous rain or snow from Saturday. A few wintry showers may affect south-eastern coasts, but most places will be dry and bright with a good amount of sunshine breaking through. Winds ease in the east, but it will feel cold, with daytime highs of 0 to 4C.