Met office
UK Outlook for Wednesday 12 Dec 2018 to Friday 21 Dec 2018:
Many will be dry, settled but cold through Wednesday and Thursday with eastern and southeastern areas often fine with some sunshine. Elsewhere, skies may perhaps be cloudier with western parts seeing rain and strengthening winds, with a risk of hill snow in the north. Through the remainder of this period there is a fine balance between colder air to the east and milder air in the west. Overall, it is likely to be changeable with showers or longer spells of rain at times, with the threat of snow over high ground. Northern and some eastern areas may remain drier with the best of the clearer weather, leading to overnight frosts. Overall, temperatures are likely to be close to normal, but coldest in the east and mildest in the west.
UK Outlook for Saturday 22 Dec 2018 to Saturday 5 Jan 2019:
This period, which includes Christmas, is looking fairly changeable with showers or longer spells of rain, possibly wintry over higher ground, less so in eastern and southeastern parts of the UK. The best of any settled and drier conditions will probably be across northern parts of the country during this period, where overnight frosts are likely. However, later in the month and into the New Year, there is the chance of seeing high pressure becoming established close to the UK, bringing more settled conditions, although there remains some uncertainty, with an unsettled and westerly airflow equally as likely into the New Year. Temperatures overall look rather mixed, but on the whole generally near normal.
https://www.metoffice.gov.uk/public/weather/forecast