BBC monthly outlook
Saturday 28 July—Sunday 5 August
An unsettled, cool weekend then drier next week
In a significant change to the weather a lot of the country has had so far this summer, it will be cooler, windier and wetter this weekend. This is due to a complex Atlantic low pressure system which will lie close to or across the north-west of the UK throughout the weekend. Saturday will see showers and rain affecting many areas, but with some sunny spells in between. It will be a windy day, with winds gusting to 40-50mph in some areas, something most of us haven't seen for many weeks. Compared to Friday, when temperatures reached the mid-to-high twenties Celsius in many areas, Saturday will be a cooler day with highs generally between 20 and 25 degrees Celsius. Sunday will see the unsettled weather continuing and it looks like rain will be more widespread and persistent. It could be a rather cloudy and wet day for parts of England and Wales. It will be windy too, with winds perhaps gusting to around 50mph again. And it will be cooler than Saturday, with highs generally in the high teens or low twenties. Quite a change to recent days.The start of next week looks changeable and relatively cool for most places as low pressure continues to influence our weather. However, the low is expected to weaken and as we go through the week high pressure will start to return, bringing drier and more settled weather. It will warm up in the south with temperatures above average by next weekend. There is some uncertainty over how far north warm air will push though, and Scotland could see temperatures remaining nearer normal It should become drier and less windy even if it doesn't warm up.
Monday 6 August—Sunday 12 August
Dry and warm in the south, cooler in the north
Medium range weather model output has shown a signal for high pressure to lie across West and North West Europe during this period. This model output has some support from analysis of similar situations in the past which give us higher confidence than we might otherwise have. The pattern for the week will be similar to the end of the previous week, with the south of the UK generally warmer than average and the north seeing some warm weather, but also some cooler interludes. The north is also more likely to see rain than the south and could see some relatively windy days too. As ever, the further we look into the future, the more uncertainty there is. In this case, we think that there is a roughly 30% chance that the high pressure we expect to be over the UK could either be weaker or further west than in our favoured forecast. In this case, we could see wetter, windier and cooler weather for the UK, although even then the southern half of the country would see the driest and warmest weather.
Monday 13 August—Sunday 26 August
Will the dry, warm weather continue?
The level of uncertainty increases further as we head into the second half of August, with differences in forecast data meaning that confidence in the forecast is medium at best. It looks likely that southern parts of the UK will remain under the influence of high pressure, so should see relatively settled weather with temperatures above normal. Northern areas are more likely to see westerly winds bringing weather systems in from the Atlantic so are more likely to see temperatures near normal, although there could be some warmer spells too.With high pressure expected to be near the UK, it looks to be drier than average across the country as a whole. However, we do expect there to be a chance of rain moving in from the Atlantic at times, mostly across the north of the country. The most likely alternative scenario would see low pressure replacing the ridge of high pressure, which would lead to cooler, wetter and less settled weather in most areas. This would not be too unusual, as very dry summers in the UK are often followed by wetter weather in September.
Next Update
Will the details for the second half of August become any more certain?
https://www.bbc.co.uk/weather/outlook