The heat continues again tonight, nights are very uncomfortable it has to be said

Originally Posted by: Matty H 

Brilliant isn't it?

We have a large tower fan. Feels lovely

Originally Posted by: Gooner 

So do we Matty but it drives me bloody potty , I switch it off when I get into bed

Long spells of sunshine, blue skies, fresh westerly breeze, max of 24c.

Current synoptics are just about perfect for NE Fife - wish the high wasn't going to build in later in the week, thereby increasing the haar/low cloud risk.

That has been the norm in my back garden for a week now , it is a heatwave in my book already

A 'shade' over 25C here today, but felt much hotter than of late, thanks to very little ifor a change! Perfect photography weather, for BA's first A380 making her first visit to Manston, accompanied by 2 Reds

According to Ian Fergusson, the hazy skies of late could be down to the forest fires in Quebec, with the smoke getting trapped within the high pressure.

Just where the planes' afterburners kick in.

I think it is just the fact that there is a vast expanse of tarmac and concrete which gets heated up by the sun and warms the surface layer of air. Even with a well shielded sensor, it will still be affected by all that warmth.

But you get a similar local effect with other surfaces too, for instance I was at Frensham Pond today which is in a dip (obviously) and has lots of bare dry sand that gets heated up by the sun. I bet if you put a proper Stevenson screen out there in the middle of the "beach" it would be a degree or two higher than surrounding areas.

Plus Heathrow is in one of the generally hottest parts of the UK anyway. In summer months the maxima usually go to places around the M25 to the west of London, e.g. Northolt, Wisley, Heathrow...

Very warm up here to day with Hull reaching 28c.

A vast swathe of high cloud has moved up from the south, spawing over central France:

http://www.sat24.com/en/gb?ir=true

While the surface synoptics do not support that airflow, the upper air charts show a weak circulation over France with southerlies up the western side - so that's probably what's driving that high cloud along.

http://cdn.nwstatic.co.uk/gfsimages/gfs.20130715/12/06/hgt300.png

There's the chart to show what I'm talking about

What's creating the high cloud in the first place? Well something is seeding the development, which might be either anomalous dust (Saharan?), unusual amounts of aircraft fumes (unlikely) or smoke particles from the Canadian fires, which could have wrapped around our high and then slid down across France from the NE. That last one could be the most likely IMO.

The effect of that high cloud looks to be to keep temps up into the high teens widely, with 21°C a possible minimum in London. The question is, will it clear by tomorrow? Some forecasts have my location cloudy but in the high-20's tomorrow, which can only be if it's thin high cloud.

Yes I remember during Summer 2003 and 2006 sat here in this study room sweating my arse off, not done that at all this time. During this spell I've only sweated when first waking up in the bedroom but that's only because of a biggish duvet cover on us and the room being over 25C.

24.2C here today. I don't think we are going to get any noteworthy temperatures from this spell which I'm not bothered about. What I am disappointed in the amount of cloud. I got 10 hours sun today but there was a huge amount of cloud just to the north which kept encroaching on us. 

There's just been far too much cloud and very little clear blue skies throughout the whole spell. The best days here were the 5th and 6th. Since then no day has managed even 11 hours of sunshine and the average has been only 7.8 hours sun a day - not even 50% of possible despite high pressure being almost right over us the whole time. The best July's have averaged more than that for the whole month, including periods with less settled synoptics. 

This will be most of us tonight . . .

lol

I'm too hot even with the covers off

Or maybe it is just that hot. It definitely feels it. With the tarmac and airplane action, I'm surprised it doesn't get hotter than it actually does. Northolt and Wisley (much more rural) usually come fairly close.

Been keeping a close tab on this heatwave for the UK, it needs to ramp up on the excitement levels a little.

When we get a long heatwave here (temps pushing 45c) a southerly buster moves up the coast guarenteed after at least a few weeks, the temp gradient can be amazing with a morning temp of 40c and falling to 17c after the change! With the change comes a massive roll cloud, storms and big hail before the heatwave rebuilds again for another reload.

If I were in the UK I would want to see some instability start to grow. Plenty of the UK summer left for another heatwave reload

Enjoy it anyway, make the most of it.

When I drove back via M25 the temps was around 32-33C on the A3 until Junction 14 on M25 the temps rose to 34C briefly before dropping back to 32C then 31C on M4 toward Slough.

but equally also go to place's like Solent, thorney, otterborne water works, or... gravesend, manston, hurn.

But i do think though you are bang on the mark in your opening paragraph :)  However as somebody else has mentioned (jokingly i suspect) i think it could be effected by the plane's. I estimate the station to be about 150m from the north runway.

https://maps.google.co.uk/maps?safe=off&q=51.479++-0.449&ie=UTF-8&hq=&hnear=0x4876723630cd76f1:0x938faf73ad58c7fa,51.479++-0.449&gl=uk&ei=gJzkUYrwH82X0AXkn4CoBg&ved=0CDIQ8gEwAQ

This is where the Heathrow station is located:

And here is the station itself: