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This is an in-depth Met Office UK Weather forecast for the next week and beyond.
This week's heatwave - the third for many - will be less hot and less humid compared with the last heatwave. But why? What makes this heatwave less hot and humid? How hot and humid will it get? How widespread will the heat become? And how long will it last?
Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
This week's heatwave - the third for many - will be less hot and less humid compared with the last heatwave. But why? What makes this heatwave less hot and humid? How hot and humid will it get? How widespread will the heat become? And how long will it last?
Bringing you this deep dive is Met Office meteorologist Aidan McGivern.
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00:00Heat wave number three is here, but how does it compare with that extraordinary heat wave
00:05we experienced at the end of June? How hot and humid are we expecting it to be during
00:10the next few days and nights? How widespread will the heat end up, and how long will this
00:17heat wave, or at least this high pressure, last?
00:21Welcome to the Met Office Deep Dive. Thank you for joining me. If you enjoy these in-depth
00:26discussions of the Met Office forecasts, then please do hit subscribe on our YouTube
00:31channel, thumbs up, send us a comment, ask us a question, we try and answer them in the
00:36Weather Studio Live on Fridays. This week I'm mostly going to be making comparisons between
00:41this week's heat wave and the end of June heat wave. Fully conscious that not everyone is
00:48experiencing a heat wave at the moment, however, for most places we are expecting it to turn
00:55drier, brighter and warmer over the next few days. And so I'm going to be covering temperatures
01:00across the United Kingdom, how high they're expected to be, the humidity and how long this
01:06fine weather will last. But first, I want to make comparisons with this heat wave compared
01:12with the extraordinary hot and humid spell that we had at the end of June, because that
01:16really was an intense spell of summer weather, quite unprecedented in many aspects of the
01:23weather. And this heat wave is more of a classic summer heat wave for the UK, the type of summer
01:32heat wave we've come to expect in recent years. So why are there differences, how does the heat
01:38and humidity compare and how long will it last? First off, let's make a comparison with the pressure
01:44chart and the jet stream, because the main ingredient you need for heat waves is high pressure both
01:51at the surface and higher up in the atmosphere. If you have high pressure at the surface but
01:56low pressure higher up, then that can force the air to rise, that causes mixing of the air
02:02in its lowest layers and so the hottest air at the surface tends to mix out with air higher
02:06up and it can also lead to cloud development which limits temperature rise. So for a heat wave,
02:11ideally you need surface high pressure and high pressure way up in the atmosphere where the
02:16jet stream lives and you can tell how high the atmospheric pressure is at the jet stream level by
02:22the movement of the jet stream around the planet. And this big ridge in the jet stream on Wednesday
02:27morning indicates a big high pressure over the UK at jet stream level 25-30,000 feet or so.
02:36And this ridge of high pressure at the upper atmosphere coincides with a surface high pressure. So that's
02:43the setup for Wednesday the 8th of July. If I go back in time to the 25th of June, you
02:50can see it's
02:51remarkably similar. Jet stream well to the north of the UK, this big ridge in place dipping south over the
03:04surface high pressure to form. There are some subtle differences however and they're more notable if
03:10we put on the temperatures at 5,000 feet or 850 hectopascal pressure level and that's a level that
03:18it's useful to look at the temperatures because it gives us an idea of the characteristic of the air
03:23mass. And this air mass that we saw on the 25th of June was notably hot not just for the
03:29UK
03:30but also considerably hot across a large part of central and western Europe, especially France and
03:38Germany of course. National records were broken for many European countries. If I go back to Wednesday,
03:45it is hot but the distribution of the heat is somewhat different and it's less intense. The heat
03:53is more focused over south-western quarters of the UK towards the sea and ocean areas, the Bay of
04:00Biscay and France and Spain and so on. Less hot across France and central parts of Europe. So subtle
04:07differences in the shape of the jet stream and the surface high have led to this difference in the
04:14distribution of the heat. And it's not just about comparing these two snapshots, it's a good idea to
04:21get an idea of how the atmosphere evolved up to these points. So we could do that by looking at
04:28air mass trajectories. So we've shown these on the deep dive before and in the weather studio live and
04:33so on. And essentially what we've got here is a snapshot of the 25th of June and over here it's
04:40the 8th of
04:41July and these lines all end up over London. London being the hottest part of the country for both these
04:51time periods. But whilst these lines end up over London you can trace them back five or six days and
05:00see
05:00where the lines came from. Now it's fairly straightforward for this week. The lines are almost all coming from
05:06the mid-Atlantic. Now these lines are coloured depending on the height that they end up being
05:12on the day in question. So the day being the 8th of July on the right here. The darker blues
05:19are the
05:20air at the surface on the 8th of July and then the lighter blues and up to the yellows that's
05:25the air
05:26at about 500 metres or a kilometre above the surface. So you can see where that air at different levels
05:33on the day in question has come from. Now the 25th of June the air has come from all sorts
05:40of different
05:40directions. The darker blues here that surface air came from the mid-Atlantic but some of these other
05:45colours the higher up air came from further below further south across western Europe, south western
05:53parts of Portugal and Spain and out towards the Azores and so on. So a much more mixed origin of
06:03the different levels of atmosphere on the 25th of June and really important what happens to that air
06:12over the five to six days in which it travels towards London. Now this graph here shows the height
06:19of those different levels of air and you trace back from the day in question the 25th of June
06:27back five or six days and you can see that some of these parcels of air came from what three
06:35four
06:36almost five kilometres high over the Atlantic and then they progressively as they entered that high
06:44pressure at the surface and higher up got squeezed got compressed so you can see how that air just got
06:51more and more compressed and that's what led to it heating up so yeah that's the primary cause of
06:58heating both on the 25th of June and with this air that's coming in for this week it's air that's
07:05sinking under high pressure but the air this week hasn't come from as high a lot of these lines
07:11restricted to one to three kilometres above so there was actually more compression of the air more
07:17sinking and that's because the high pressure in the upper atmosphere and the high pressure at the
07:21surface were even stronger at the end of June compared with this week so there was more sinking
07:28of the air more compression and more heating at the end of June compared with this week
07:34and that likely was the primary cause of higher temperatures we ended up recording temperatures of
07:4334 35 celsius widely by the end of that week and you know the top temperature was in excess of
07:4937 celsius
07:51now this week we're talking about temperatures at widely 32 33 celsius and in places 34 or 35 celsius
07:58so the primary difference here in the temperature is that there's more sinking at the end of June compared
08:06with this week but the origin of this air is important as well because these different um parcels of air
08:15came from more humid sources so some of the air came from Iberia some of the air came from uh
08:22Bay of
08:22Biscay parts of the Atlantic that are warmer than central mid-atlantic here so central north Atlantic here
08:30so the air source was more humid and in many ways it was warmer and it underwent more compression
08:38at the end of June compared with this week but it's that compression that is the primary cause of
08:44of the heating it's just that at the end of June there was a bit more of a southerly component
08:50more humidity extraordinary levels of humidity and a lot more heating as well so yeah
08:58that's the icing on the cake really whilst it's a similar cause the high pressure and cloud-free skies
09:06of the higher temperatures with both heat waves this heat wave had air coming from a warmer and more
09:13humid source originally which was really the icing on the cake but another difference between the two
09:20heat waves is the preceding weather now this is where this heat wave is i say benefiting you know allowing
09:31temperatures to be higher from drier weather leading up to it so we've got the rainfall amount through this
09:40summer so far and the date on the x-axis on the bottom there first of June quite a wet
09:46start to
09:47June first 10 days or so you can see these rain spikes this by the way is southeast England and
09:53central
09:53south England because that's where the highest temperatures have been and are expected to be
09:59wet start to June then not much rain but it's around this period here that the last heat wave
10:07occurred and there were some rain spikes there was a notable wet spell at the very start of that week
10:13on the Monday morning when some thunderstorms moved through and so that wet the ground wetted the ground
10:21up and as a result that heat wave started off with relatively moist soils and so on and that meant
10:31that despite the cloud-free skies all that sunshine the solar energy had to you know go to work
10:39evaporating some of the moisture on the ground so that did limit temperature rises and you might
10:46remember from that heat wave there were some really quite ridiculous temperature forecasts coming
10:53through in some of the weather models some of the weather models that week were suggesting temperatures
10:57of 40 41 42 celsius that week those temperatures given how um how much heating was going on with the
11:09compressing of the air and the hot and humid source of air there was the potential for temperatures
11:16like that if the ground was bone dry but the ground wasn't bone dry so that's a bias that we've
11:24noticed
11:25with certain computer models is that they often assume the ground is drier than it is and end up
11:32predicting higher temperatures as a result especially given that the start of that week we had much more
11:39widespread thundery rain than the computer models knew about so one of the things that the models were
11:45suggesting that week was that the air was very the ground was very dry we'd see temperatures into the
11:51high 30s low 40s but of course it wasn't as dry as they thought so meteorologists here at the met
11:58office
11:59we were talking about a temperature forecast most likely high at the end of that week of 39 celsius
12:06give or take two degrees it ended up being a little short a degree and a half short of that
12:12uh but yeah we we weren't necessarily believing the model projections of 42 celsius some of them were
12:21feeding some weather apps of course so they were in the public domain but our official forecasts weren't
12:28giving numbers of 41 42 celsius we were deliberately knocking those temperatures back because we were
12:35expecting that the models um were overestimating how dry the ground was but of course we didn't peg them
12:44back quite enough this week is a completely different ball game because we're now here and we've had very
12:53little rain for a couple of weeks in south eastern central uh england and so yeah the computer models estimates
13:04of
13:04how dry the ground is right now are about right and so they're unlikely to be overdoing temperature
13:10predictions quite as much so yeah less potential in the atmosphere to give high temperatures or on
13:17unusually high temperatures high 30s this week but at the same time the ground is drier so
13:24we're not likely we're likely to see temperatures rise further as a result of that another thing to point
13:31out sea temperatures have warmed up of course so we're now surrounded by warmer waters there is a
13:37marine heat wave surrounding the uk unusually high sea temperatures and this is the end of june
13:43temperatures widely around uh uk waters around 17 18 celsius and then skip forward to the time being
13:52and temperatures in excess of 18 celsius that's what these colors are suggesting 18 19 20 celsius across
14:00the south and southwest of the uk so that's going to help temperatures rise a bit further this week so
14:08yeah june 2026 huge potential heat and humidity in the atmosphere because of the very large and dominant
14:19area of high pressure that expanded over parts of france and led to really high temperatures low 40s across
14:26france and other countries around the continent but the the true potential of those temperatures
14:34wasn't quite realized in the uk because of the damp surfaces that we started the week with
14:42this week we've got dry ground we've got lots of sunshine the potential of the atmosphere isn't quite
14:48as high we haven't got quite as high an area of high pressure at the surface and and higher up
14:54we haven't
14:54quite got the compression of the air so those are the key differences between this week and
15:02and the end of june another key difference or actually this is quite a similar theme is that
15:10the heat wave has already started in the south we've had a few days across southern england south wales
15:15of high temperatures whilst northern england northern ireland scotland has been prone to a stronger
15:22breeze a lot more cloud and outbreaks of rain but that's all going to change from wednesday you can
15:29see this big ridge of uh in the jet stream this extension of high pressure from the south across
15:36many parts of the uk and we can follow that forward still some weather fronts bringing cloud apache rain into
15:43the far north and northwest of scotland where it will always be cooler but that even that disappears by
15:50the weekend as high pressure shifts and begins to migrate northwards and by sunday you can see that
15:57high pressure is centered over northwestern scotland with more of an easterly breeze for england and
16:04wales that's going to do two things let's first of all look at the weather over the next few days
16:08and
16:10how that will change so yeah still a lot of cloud and some damp weather around on tuesday skipping forward
16:17to thursday you can see a lot of that cloud thins and breaks northern ireland much of scotland
16:21and certainly for a large part of england and wales it's clear blue skies it's strong spells of
16:26sunshine still some showery light rain for the likes of lewis and harris and a few spots there over the
16:31west highlands but nowhere near as much as we've seen during the weekend and the start of this week
16:37similar into friday and the weekend you notice there are some quite beefy showers developing there
16:44across northern england into the midlands and always the chance of some of these showers through the
16:48weekend migrating north across parts of france into the southeast of england but on the whole
16:56the very dry and bright weather that we've got in the south at the moment that's going to spread
17:01much more widely northwards and temperatures will rise as a result so that's the first thing that's
17:07going to happen as the high moves north the second thing that's going to happen if i put the winds
17:12on
17:12is that we'll get through the weekend a stronger easterly breeze and that will limit temperatures
17:20more along the eastern side of the uk and some low cloud will make an appearance some um fret and
17:28har eastern scotland there northeast england so yeah some of these coastal parts bordering the north sea
17:36increasingly cloudy through the weekend and feeling much cooler because of the cloud
17:40and the longshore breeze but further west we'll keep the high temperatures western scotland increasingly
17:48the place to be yeah very damp weekend wet start to the week but from wednesday thursday increasingly
17:55dry and bright widespread sunny skies then by the weekend let's take a look at temperatures and how
18:00they're going to change over the next few days so on monday we had 34 celsius recorded in
18:06headington tuesday similar temperatures fairly widely but perhaps a degree or so down 33 celsius
18:15that's what we're expecting at the time of recording we'll know of course by the time this deep dive is
18:20online wednesday temperatures rising once again i think likely to see quite widely across central and
18:31southern england high 20s low 30s top temperature 32 33 wouldn't be surprised if there's a 34 but
18:41importantly further north northern england mid to high 20s into the south and southwest of scotland
18:48low to mid 20s and northern ireland 23 24 celsius so things are warming up as that dry and brighter
18:57weather
18:57spreads further north and that continues into thursday thursday thursday's a hotter day for
19:03most of the uk you can see this heat expanding north mid to high 20s widely across england and wales
19:11and in some places 32 to 34 celsius on thursday so just to give you an idea there of the
19:20distribution
19:21the heat still hottest across central and south eastern parts of england but further north into
19:25scotland you know 25 26 celsius possible northern allen 25 celsius possible on thursday and into friday
19:33so again another hot day on friday and this is a long run of temperatures in excess of 30 or
19:39in some
19:40places in excess of 32 33 celsius we don't normally get such a long run in which temperatures exceed those
19:48numbers not quite reaching the dizzy heights that we saw at the end of june not seeing the high 30s
19:53but it's a fairly long run nevertheless by the time we get to sunday however having seen those temperatures
20:00peak on friday and perhaps saturday the heat becomes more focused towards the west the coast of eastern
20:09england the southeast eastern scotland a bit cooler because of that onshore breeze and the additional cloud
20:18but you can just pick out low to mid 20s across western scotland parts of northern ireland and so
20:24on northwest england west wales so the heat is moving and that's clear when we look at the temperature
20:32compared with average on this graphic here this redistribution of the heat is very apparent when you
20:39look at how temperatures compare with average we've got tuesday wednesday thursday friday on screen the
20:45darker reds indicate temperatures well above average in fact we can take a look at the key
20:50here so on tuesday we've got temperatures uh seven degrees above average in places wednesday much more
20:59widely warmer than average across england wales northern ireland still western scotland a little below
21:05average but going further ahead into thursday it's simply the northwest of scotland where we keep below
21:13average temperatures because of the cloud but elsewhere this heat expands across central parts of england
21:19and into southern scotland eastern scotland northern ireland as well let's skip ahead to saturday the
21:27cooling trend in the east is really apparent much warmer than average for wales and western england
21:34back to around average for eastern parts of england cooler than average for eastern scotland so
21:39yeah as those winds switch to easterdies through the weekend a cooling trend initially in the east
21:45whilst we keep temperatures into the low possibly mid 30s for western and southwestern parts of the uk
21:51and then that cooler air begins to affect all of us two other things quickly before i look at the
21:58long
21:58term trend one overnight temperatures not as high as the end of june heat wave primarily because
22:07the humidity isn't as high so i mentioned how the origin of the air at the beginning
22:13um for this heat wave comes from a cooler and less humid source and that's really important when you
22:20look at overnight temperatures this week they're still going to be warm you know any other year this
22:25kind of heat wave would be particularly notable for its high temperatures high overnight temperatures
22:30its duration its extent and so on but it's nowhere near as intense nowhere near as humid as the end
22:37of
22:37june heat wave therefore the kinds of impacts that we saw back then health related impacts infrastructure
22:44impacts not expect to be on the same scale but here's just a snapshot thursday morning these are
22:49the kinds of temperatures probably overdoing it a bit for london there i suspect that mostly temperatures
22:54will be between 16 and 20 celsius across the uk so still warm but we're not looking at the low
22:5920s
23:00overnight those are the temperatures that we saw at the end of june and the dewpoint temperatures so this
23:06good indication of humidity well at the end of june dewpoint temperatures were in the high teens and and
23:14low 20s widely mirroring the overnight temperatures this heat wave much more comfortable low teens mid-teens in
23:23places so still hot and humid still notably hot and and a long lasting heat wave just not as
23:31extraordinarily intense as we saw then on the duration of this heat wave well let's skip ahead
23:39to the start of next week because i mentioned that through the weekend we'll see the high moving north
23:45and this is the control run from the european model and it shows that high sitting to the north of
23:51the uk
23:51isobars a bit more tightly packed across england and wales they're indicating this easterly breeze
23:56so cooling trend from the east through the weekend and into the start of next week still above average
24:02temperatures still widely sunny skies still very warm for many away from that east coast but not as hot
24:10and really playing that forward that high pressure just meanders around northern parts of the uk so yeah
24:16scotland northern ireland northern england have been slow to join in as far as the dry bright
24:23settled spell is concerned but it's going to last potentially longer across northern parts of the uk
24:31compared with the south because by the time we get to the end of next week again most of the
24:36most of the uk high pressure is nearby we've still got this easterly airflow
24:41it's not as hot but it's most settled towards scotland because that's where the high pressure
24:49is closer low pressure over the continent may well start to bring something a bit more changeable
24:59more showery more thundery as the week goes on next week but very slow changes through next week
25:06actually one interesting thing to quickly show you the jet stream this is sunday you can barely see it
25:13so atlantic activity really weak this high the dominant feature and where that ends up will be
25:21crucial through next week it's only going to be moving very slowly but where it ends up is going to
25:27be really important for determining the distribution of the temperatures which is clear when you look at a
25:32graphic like this i showed you the control run from the european model well this is all the runs from
25:39the european model out on display wednesday the 15th of july saint swithern's day of course 2 pm and it
25:47shows the pressure and the temperatures you can see for most of these high pressure is somewhere close to
25:53the uk but where that high is well there are subtle changes and and that determines the colors on the
26:00map
26:01which represent temperatures so there's there's one here that's uh let's see number 32 that's got high
26:08pressure well to the northwest and it's got this plume this low pressure but a plume of heat coming up
26:14from the continents that's one option for next week high pressure well to the northwest another option
26:20is for the high to be sitting over northern scotland perhaps um and to be giving more of an east
26:29to
26:29northeasterly wind so more widely cooler air this option here number 50 that's got a brisk northeasterly
26:36wind so much cooler air and just to compare those two we've got 32 that shows a plume of heat
26:43coming
26:44in from the continent on that wednesday skip forward a bit there we go it's got temperatures next wednesday
26:52of the high 20s low 30s in places because we've got this plume of heat coming up from the south
26:58it's still settled for many parts of the uk i wouldn't be surprised if there's some thunderstorms
27:02associated with this plume though because it's got low pressure high pressure is way out here
27:09look at that way out there now the other option number 50 high pressure in virtually the same place
27:15but a subtle difference in the isobars they're bringing cooler northeasterly winds in
27:20and temperatures more limited the low to mid 20s so really slow changes through next week high
27:28pressure dominant across the mid and east atlantic around the vicinity of the uk but where that high
27:37ends up will determine whether we get a cool northeasterly or a plume of warmth coming up from
27:43the south with some thunderstorms and those are the things that are in play for next week will be
27:49really interesting to see how they evolve but that's all from me we'll have more details of
27:54course on the long-term forecast uh in tomorrow's 10-day trend do join us for that but uh yeah
28:00thank
28:00you for you for your time today i hope you enjoyed it bye bye for me
28:03you
28:04you
28:05you
28:05you
28:05you
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