BBC monthly outlook
Summary
Often unsettled, a few dry and warm spells likely
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Saturday 29 June – Sunday 7 July
Changeable week, but often dry in the South
A hot start to the weekend for many, with southerly winds bringing in some of the hot air over France to much of England with highs expected to be in the upper twenties to low thirties. Sunny and humid, but with growing clouds in the West as a cold front pushes in Saturday evening and night. This front will bring some heavy showers and thunderstorms with frequent lightning to Scotland, Northern Ireland, North England, and North Wales. Staying dry further south and east.
The cold front passes overnight, leaving Sunday feeling noticeably cooler than the hot Saturday (although highs will be around average). A fresh westerly wind with mostly sunny skies and scattered showers in the west and north will persist through Monday. High pressure will then begin to build in through midweek, keeping things more settled, drier, and a touch warmer. However, this too will be short-lived as the high pressure centre weakens in the second half of the week, allowing a low to move in from the northwest. This will be showers and cloudier skies, mainly to northern and north-eastern areas with the south and southwest staying dry. Cooler with a fresh north-westerly wind.
Heading into the weekend, some uncertainties begin to grow, and low pressure is expected to linger over or near Scandinavia with a ridge of high pressure in the Atlantic. The main issue is now extensive high pressure ridges in the Atlantic will get, with a potential for the UK to see a fairly settled and slightly warmer weekend, but showers will likely still be a factor for the north-eastern counties.
Monday 8 July – Sunday 14 July
Settled start, but turning wetter and cooler later
High pressure nearby to the west should keep the first part of the week settled, although winds will be out of the northwest bringing in some cooler air and rain to the far north of Scotland, western Scotland, and Northern Ireland. Low pressure systems over Scandinavia are expected to gradually shift west and be centred more over the UK by the middle of the week and into the end of the week. This will shift winds to more westerly but also bring a return of the slow-moving fronts that plagued the UK throughout June.
All this means that after a mostly dry start to the week, temperatures will tend to stay a bit below average as the weather turns gradually wetter for most. The best of any dryness will be in the South and Southeast, but even here occasional rain is likely. However, high pressure ridges will likely linger into Central Europe from the southwest, and these will tend to keep fronts and low pressure systems more in the northern half of the country than the southern half. There is a risk to the forecast (25%) that high pressure ridges will remain for extensive across the UK through the end of the week. This would mean things will generally be warmer, drier, and calmer overall. Temperatures in this scenario would tend to fall above average, with a potential for some very warm days later in the week.
Monday 15 July – Sunday 28 July
Often unsettled and cool; occasionally warmer
Low pressure tracks are expected to remain across North Europe as the jet stream - a ribbon of fast-moving air in the upper atmosphere that drives weather systems - stays further south than normal for summer. Large low pressure systems will likely slowly drift westwards towards Iceland through the end of July, keep things generally unsettled in the UK with slow-moving fronts and cooler westerly or north-westerly winds persisting.
However, the hotter summertime temperatures in the sub-tropical Atlantic will keep the large high pressure centre near the Azores strong. This will occasional extend northeast into Central Europe, and between low pressure systems will even reach into the UK at times. This will lead to a changeable weather pattern with a high degree of weekly variability in both rainfall and temperatures. The general weather pattern is expected to be mostly unsettled, but with a few dry and settled spells that bring in some warmer air. These most often in the south. There are currently no strong signals for any prolonged heat or dryness.
The main alternative scenario to the forecast for late July is that high pressure continues to be more extensive into the UK, resulting in a warmer and drier trend. This is summertime, and the Azores high pressure centre is strong throughout the month, so there is a chance (30%) that late July may turn a bit more summery than June and early July. In this situation there is a risk of another heat wave as well, and these are more common in late July.
Further ahead
We will continue to look at the unsettled weather pattern through July to see when things may finally dry out. This will give us a better picture of any late July heat as well.
https://www.bbc.co.uk/weather/outlook