BBC monthly outlook
Summary
Dry for many to end December
Saturday 22 December—Sunday 30 December
Often cloudy and misty but dry in the south
This weekend, Saturday will be the drier and brighter of the two days for many with sunny intervals although the west and northwest of the UK will also have scattered showers. On Sunday, England and Wales will be mostly cloudy and wet with outbreaks of rain. Staying drier for much of Northern Ireland and Scotland, though, with some bright spells but a risk of fog both early and late in the day.
Next week will see a change in the weather as a high pressure area moves closer to the south of the UK. Many central and southern areas of the UK will have often dry and relatively calm weather, including on Christmas Day. However, it looks as though there could be a lot of cloud at times with a risk of mist and fog in places, particularly through the nights and into the mornings. Further north, it is likely to be breezier at times with occasional rain. Temperatures will mostly be a little above the December average although local night frosts cannot be ruled out, particularly in the south.
Monday 31 December—Sunday 6 January
Mostly dry and settled; possibly wetter later
Mostly dry and settled conditions are expected to persist into the first week of January, thanks to an area of high pressure often nearby to the south. However, the high pressure ridge will also bring the continued threat of fog at times, particularly to central and southern areas of the UK.
Cloud amounts are uncertain. The cloud may be thick enough at times to produce occasional drizzle. However, where any lengthier clearer periods develop, there is also likely to be some patchy night frost. Overall, temperatures are expected to be near to the normal for this time of year. In the far-north, temperatures are favoured to be a little above the seasonal average with more of a breeze and a lower risk of fog. Towards the end of the week, we may see high pressure move further away to the south, bringing an increasing chance of wetter and breezier conditions then.
Monday 7 January—Sunday 20 January
Breezy and wet. Mild at first, then colder.
In the second week of January, we expect somewhat breezier and wetter conditions compared to the first week. Low pressure areas are likely to move closer to the UK at times, bringing rain and brisk winds at times. The risk of fog will become much lower too. Temperatures are likely to be variable but, on average, a little above the normal for this time of year.
Into the third week of January, we expect low pressure areas to still be close to the UK, continuing to bring unsettled and breezy conditions at times. However, low pressure areas could well start to track further south across the UK. Therefore, the wettest conditions are favoured to be over the southern half of the UK. Over northern areas of the UK, it should turn less wet but somewhat colder at times. Indeed, there looks to be an increasing chance of some snow at times for northern areas of the UK. The main uncertainty to this forecast is on the extent of colder air by the middle of January; there is a considerable risk that significantly colder conditions extend to many areas by then.
Next Update
Could we see colder weather arriving from the north for the middle of January?
https://www.bbc.co.uk/weather/outlook