BBC monthly outlook
Summary
Some hot weather at times, but lows threaten
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Monday 10 August – Sunday 16 August
Hot conditions, but thunderstorms likely
This weekend, high pressure will continue to build across the UK, bringing plenty of dry, sunny weather. A northeasterly breeze with take the edge off the heat a little, but highs will be into the 30s Celsius across southeast England. It will rather humid too, making for some rather uncomfortable nights, with temperatures still in the low 20s Celsius overnight for parts of England and Wales. Over the weekend, there is a risk of some showers and thunderstorms developing, but this risk heightens as we head into the new working week.
Monday and Tuesday could see clusters of thunderstorms pushing up from the south, with heavy downpours and frequent lightning a distinct possibility. On Wednesday, further showers and thunderstorms look possible, most likely across southern England, with an additional risk of downpours and frequent lightning. The risk of thunderstorms should then shift away into the near continent into the second half of the working week, as the ridge of high pressure shifts eastwards. This will allow temperatures to moderate heading into the end of the working week as winds shift, but it will still be on the warmer side of average.
For next weekend, high pressure should build in from the southwest, bringing largely dry and fine weather, and temperatures slightly above average.
Monday 17 August – Sunday 23 August
A chance of another hot spell or heatwave
Around this period, high pressure is likely to be near to the British Isles, or out to the northeast over Scandinavia. This should bring plenty of dry and settled weather, perhaps with multiple sunny days for many parts of the UK.
Whilst high pressure is likely to be towards the northeast, there is the potential for low pressure to become situated out to the west of the UK. This set-up can lead to intense warming across the UK, as warm air tends to plume up from the south. As a result, there is the chance of another hot spell or heatwave during the week. After the heatwave conditions earlier in August, further hot weather could see temperatures trending much warmer than average for August as a whole.
However, with low pressure out to the west, fronts may creep into Northern Ireland and Scotland, bringing some wet spells of weather here. There is also the risk that low pressure is instead more influential right over the British Isles, bringing unsettled weather more widely across the UK.
Monday 24 August – Sunday 6 September
Wetter in the north, mostly dry in the south
Through late August and early September, areas of low pressure are expected to track over Iceland and near to the north of the UK, with fronts glancing Scotland and occasionally Northern Ireland at first. Gradually as we head into September, associated fronts will extend across the UK, with wet and breezy spells of weather looking likely for most. Rainy periods will probably be most frequent across Northern Ireland and Scotland, whilst England and Wales may only see fleeting spells of wet weather as fronts come and go. Southeast England will likely be the driest spot, with only the odd patch of rain likely.
In fact, a strong northwest-southeast split in the weather looks probable for this period. High pressure may ridge in from Europe to give lengthier periods of dry and warm weather over the southeast, whilst fronts pushing into the northwest will give frequent wet spells and fluctuating temperatures.
Since the UK is sat on the periphery of the two weather regimes mentioned above, there is considerable uncertainty by this point, as one weather type may dominate over the other for an extended period. There is a risk that low pressure areas track further south than expected, which would bring above-average rain to the south instead. By the same token, high pressure ridging may be more persistent and extensive over the UK, which would bring drier, warmer weather more widely across the country. Another complicating matter is that by late-August the Atlantic hurricane season is forecast to become rather active, and this can lead to large swings in the weather for the UK.
Further ahead
We will examine the complicated pattern for next few weeks and see whether there's a possibility of any further hot spells of weather across the UK.
https://www.bbc.co.uk/weather/outlook