Just hit 30C here, again still a little behind the neighbours. And I agree with Justin's asseessment... inside, at least, it's still pleasant.

The rate of increase in the curve of temperatures is, at least, slowing down. It's looking like a textbook sinewave!

Midas has the hourly data for Heathrow for 2003 and 2019 and Weatherobs for today up to 08:00 so far

There is a bit of catching up required today to beat either of these earlier records

Only 23c here with a constant stream Alto castellanos and high-level activity showing up on radar, cooler than yesterday at this point.

I'm now entering hibernation to escape this godawful heat. Please somebody wake me up on Wednesday morning when it's all over.

most of the later ones will likely be broken

28C at Biggin Hill seems to be the warmest official one so far, though it looks like PWSs are steaming ahead much more than usually. May be just where they are sited. E.g. my vineyard is already 29.2C and its warmest year to date is only 29.6C last Monday.

Biggin is an interesting on as it's on top of the downs, as is my PWS (well, half way up) so may suggest we still have an inversion lower down.

6 hrs of heating to go

Bear in mind though that Heathrow is unlikely to be a record contender today. It will be somewhere further north I think. I would expect Heathrow to top out around 37 today, but it all depends how long the heating keeps going as the really hot upper air arrives.

25.5  C here at the harbour end yet the GFS forecast put me down at 31 C by now (I guess their coarse resolution cannot handle coastal features).

Still a notable onshore breeze blowing into the house, but I'll be going out on my usual Monday morning chemist errand soon so I'm sure I'll be singing a different tune after walking in the unbroken sunshine.

Quite a few 29s at 10am. Including Cambridge and my nearest WS Stansted AP. Cambridge could be the record breaker today. 

29C here after reaching 18C over night low.

29.7C at the vineyard, meaning I've reached the hottest day of the year so far at 10.05am.

It will be the first 30C+ today since I installed the sensor last August. 

What makes this record chase even more interesting is that so many locations have a chance for the record form Kent, London,  Cambridge,  EA, East Midlands and even Yorkshire.  My punt would  be somewhere near Nottingham tmrw takes it.

28.7C here and we are at 185m - so a good degree higher down in Wye I would imagine.

28.9C already at Blackbushe, which is usually lower than surrounding stations. Feels like it is really picking up the pace now.

34.9C in Biscarrosse SW France.

Wisley the first SYNOP station to breach the magic 30

Yup, it is - just about to hit 31 now (which matches the GFS forecast, incidentally... every other model was a few degrees lower for 9z).

The other thing of note is that there seems to be a SW'ly flow at low level here, not the SE that the models have. SW'lies tend to bring higher temperatures to the likes of Medway, Sittingbourne, Sheppey and Faversham as the Downs have a bit of a foehn effect.

I'm hoping the winds will back SE'ly sooner rather than later!