BBC monthly outlook
Wednesday 15 August—Sunday 19 August
Breezy, and often wet in the north
After a rather humid, breezy day in the south, with cloud and patchy rain spilling into western and northern Britain, on Wednesday night northern areas can expect to gradually become clearer and drier. A band of fragmented rain will continue to push south-east into central and southern England, however.
By Thursday morning, central and south-eastern England will have a wet start, with persistent rain expected for a time, before the rain eases and the responsible front slowly edges into the North Sea. Northern and western Britain will have a drier and brighter day, with sunny spells but also some heavy, thundery showers moving in from the west.
Friday will see another area of cloud and patchy rain moving into north-west Britain, bringing fresh winds too. Much of England and Wales will remain dry with good spells of sunshine and some fair-weather cloud, although the sunshine may be hazy in the west.
By the weekend, a weak front is expected to straddle central Britain and Ireland, giving a lot of cloud and a few spots of rain on Saturday. Warm to the south of the front, some light showers are likely to affect western Scotland.
More widespread rain looks like moving across central or northern Britain on Saturday night and early on Sunday, but the far north of Scotland and southern England should remain dry. Warm and humid in the south on Sunday, with temperatures reaching the mid-20s Celsius in London, while the rain only slowly eases in the north.
Monday 20 August—Sunday 26 August
Higher pressure in the south
Monday and Tuesday next week will see lighter winds than preceding days, because pressure will rise to the south of the UK. However, a weak front may still bring some patchy rain to central, northern and western parts of the country, while south-eastern England sees the driest and warmest weather.
Northern Britain will see temperatures around, or slightly below normal, with a risk of a few showers developing. By the middle and latter half of the week, high pressure will attempt to ridge across the UK from the south-west.
Although there is some uncertainty regarding how widespread the high pressure will be, it looks like southern Britain will remain closest to the centre of the high, meaning a lot of dry and settled weather is expected here.
Temperatures may rise slightly above average here, with light winds and sunny periods becoming more widespread. For northern areas, particularly Scotland, frontal systems are likely to bring cloudier and damp conditions, with patchy rain at times and somewhat breezier conditions.
The cloud, rain and general westerly airflow from the Atlantic will keep temperatures below average here, although there is a chance that these breezier and cooler westerly air flows may develop further south across England and Wales for one or two days, as weakening fronts encroach south-eastwards.
Monday 27 August—Sunday 9 September
Becoming settled in September
A weak area of high pressure is likely to linger across the UK by the start of the following week, continuing warm and generally dry conditions for southern and central areas. Winds will mainly be light too, and there is a chance that the warmth could become more extensive across the UK for a couple of days during the beginning of the week, as there are signs that the high could become established right across the UK for a time.
During the second half of the week, areas of low pressure will become favoured to the north of Scotland once again, although it is uncertain how quickly this transition will occur. It is likely to become cooler for all, with temperatures falling below-normal across northern Britain.
Fronts will be encouraged to move across much of the country from the north-west, giving a wetter and windier end to the week for all areas, but especially in the north. By early September, a return to high pressure to the west of the UK is favoured, although areas of low pressure could linger for a time early on.
Therefore, the coolest, wettest and breeziest weather looks likely during the first few days of the month, with low pressure systems to the north of Scotland responsible. Then, building high pressure from the south-west is expected to bring a return to more widespread drier and settled conditions.
Next Update
Will we see some late Summer weather in September?
https://www.bbc.co.uk/weather/outlook