Wednesday saw a top temperature of 31.9C reached at Preston in Lancashire and the heatwave looks to intensify over the next couple of days, with an Amber Warning for extreme heat now in force from today through to the end of Sunday for much of England south of a line from Lancaster to Hull and parts of east and southeast Wales.
The reason why the heat will intensify across southern Britain over the next few days is because of increasing subsidence of air from aloft from an upper level ridge causing compression of air at the surface increasing air thicknesses from the near continent over the next couple of days. This leading to higher temperatures – exacerbated too by dry ground conditions, with most of the sun’s heat warming the surface layer of air rather than being absorbed by the ground.
Much of Britain will be bathed in sunshine today, temperatures under mostly clear blue skies will widely reach 30C or more inland in the warning area, including Manchester, Leeds and Cardiff, somewhere across southern England reaching 33C. To the north of the warning area, temperatures reaching the mid to high 20s across northern England and eastern Scotland. The exception to very warm and sunny weather will be across the far north and northwest of Scotland which will be cloudier and cooler – with rain moving in off the Atlantic.
Peak temperatres likely on Saturday, with highs in the mid-30s across southern England
A similar picture on Friday and Saturday too with widespread sunshine across the UK, Friday a degree or two higher across southern England with highs of 34-35C, Saturday the peak of the heatwave – with some spots in southern England likely reaching 36C. The exception to the sunny and very warm or hot conditions will be northern Scotland – where it will be cloudier and cooler – with some patchy drizzle. While Haar may affect coasts in the northeast too.
It looks to remain very warm and sunny on Sunday, very hot in the south. We will likely see an increase in mid-level cloud from the south, as a shallow area of low pressure drifts up from the southwest, with some thundery showers breaking out across northern Scotland and the far west further south. While some thunderstorms could spread into the far south later in the evening. Highs reaching 34C across central and southern England.
Turning more unsettled next week - as low pressure takes over, with a risk of thunderstorms and localised flooding
With low pressure across the UK on Monday, it will be a cloudier but still very warm and humid day, with some heavy and thundery downpours breaking out in places – which may lead to some localised flooding given the hard and dry ground. There will be some sunshine too and across eastern England – where the sun does come out it will be locally hot – with temperatures reaching the high 20s, perhaps 30C.
More unsettled and increasingly cooler conditions for the rest of next week look likely. On Tuesday and Wednesday England and Wales likely to remain warm with some sunshine but also some heavy showers or thunderstorms developing quite widely, with a risk of localised flooding. Scotland and N. Ireland turning cooler and showery as a northerly or northeasterly wind develops. Thursday onwards may start to see more of westerly flow develop, so cooler for all, though temperature closer to average for most. The Atlantic flow bringing a mixture of sunny spells and scattered showers, occasionally some longer spells of rain in places too.