BBC monthly outlook
Summary
The often wet and windy weather continues
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Saturday 20 July – Sunday 28 July
Heating up in the South next week, cooler later
A fairly unsettled Saturday will see a gradually shift into a more north-south split in the weather for the UK from Sunday and into next week for a time. Saturday will start off wet in the Southeast with some heavy showers and perhaps a rumble of thunder. This rain will clear to the east by the late morning. Scattered heavy showers will then drift into all areas of Britain from the west in the late morning, and by the afternoon a few thunderstorms are expected in central and eastern Britain. These will produce locally frequent lightning and heavy downpours.
From Sunday and through into Tuesday, high pressure building in Central Europe will keep things fine and dry in the southern half of the UK, but the northern half will see plenty of rain, which will be heavy at times. There is a risk for some local flooding in West Scotland from Sunday through Tuesday. A heat wave expected to develop in France will bring in some hot air to the Southeast from Tuesday, with temperatures well above average and reaching into the low 30s on Tuesday and Wednesday. Staying a bit cooler up north, but still warmer than this week has been.
For the second half of the week, there is some uncertainty in the forecast based on a cold front arriving from the west. The jet stream - a ribbon of fast-moving air in the upper atmosphere that drives weather systems - is unusually strong for summertime in the United States and Atlantic. This will likely result in a cold front arriving on Thursday, bringing some relief from the heat but also a risk for some heavy showers and thunderstorms, especially in the North. Low pressure will then take over, and keep things unsettled and feeling cooler through the weekend.
Monday 29 July – Sunday 4 August
Cooler and more unsettled start to August
As we head into August, there is good support for low pressure systems to become more dominant weather features for North Europe, allowing Atlantic fronts to move through the UK. High pressure is also expected to ease in the near Continent, so fronts are expected to reach into southern areas of the UK as well as the north. For the first half of the week winds are expected to bring in some cooler polar air causing temperatures to dip to near or below average for late July/early August. This will be more noticeable in the west and north, with a cooler feeling onshore breeze. In general northern and western areas will see more frequent showers and cloudy skies, with the best of the dry and bright weather being in the south and east.
Fronts will bring in short-lived outbreaks of rain to all areas at times, but there is still a great deal of uncertainty on the day-to-day specifics. As the week progresses, low pressure is expected to gradually shift slightly northwards towards Iceland, which will likely bring in a return to the north-south split in the weather. The northern half of the UK will continue to see wetter and windier weather than typical for August, while the southern half of the UK turns a bit drier and brighter, although still occasional outbreaks of rain.
Monday 5 August – Sunday 18 August
Wet and windy, but drier at times in the South
For the first full week of August, low pressure will still be very much in charge of the weather pattern for the UK. This will bring in Atlantic fronts, outbreaks of rain and occasional thunderstorms, and windy weather to mostly northern regions. Occasionally the wetter and windier weather will reach into the southern half of the country, but it will generally be drier and brighter here. Going deeper into August, high pressure looks to become more influential in Central Europe again, which will push the low pressure near the UK even further north. While northern areas are still expected to remain unsettled and stormy at times, the South will turn mostly dry and bright, with temperatures climbing to a bit above average.
There currently aren't any strong signals for prolonged heat in either the UK or Central Europe through mid-August, but there is risk that another heat wave could develop with high pressure building into the Continent. Low pressure near the UK with the jet stream overhead will tend to mean any heat waves that do form will remain south of the UK, with just a chance for a brief hot spell or two lasting only a few days. There also isn't any strong signal for a remarkably wet or cold August either. The weather is expected to remain quite changeable with temperatures tending to linger near average with only brief deviations.
Further ahead
Taking a closer look at the first half of August, we will see if things look any better for a drier and sunnier summer to appear.
https://www.bbc.co.uk/weather/outlook