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Highest reported temperature was at Hurn (Bournemouth Airport) a known poor synoptic Met Office site, although it could be worse. There is a bit of a mystery.
24 hours ending 2200 on 14 Jul 2013:
UK Highest max 0900-2100 31.0 °C Hurn
Lowest max 0900-2100 12.9 °C Lerwick
Lowest min 2100-0900 3.6 °C Katesbridge
Highest rainfall 2100-2100 4.8 mm Cassley
Sunniest 2100-2100 14.3 hours Morecambe
Last updated: 0001 on Mon 15 Jul 2013
The Met Office hourly data for Hurn peaks at 29.0C, so there is a brief peak for some reason. Looking at other data 29 or so would be fair enough. How did 2C materialise?
The three highest hourly figures are
29.0C
28.9C
28.9C
The wind was initially from the south, be an off sea breeze. Further north there was flat calm followed by a faint north westerly (I watched the clouds at one point), in general the wind was erratic.
These days it’s PVC screens housing what the Met Office call a sensor, maybe I ought to ask 2, 3 or 4 wire? Just a lump of metal where the resistance changes, placing stress on the electronics, which never get mentioned, nor the software. I’d be very interested to see full information on the dynamic response relative to mercury in glass inside painted wood.
Met Office documents have leaked the usage of peak reading, ie. noise, a lot of detail would be needed to start figuring what is going on, let alone the variations in design. This particular AWS site has paving and many other instruments close by. The possibility of RFI must be there given many radio and radar transmitters.
Calling up Chilbolton again, which once again is located quite close, peaked 29C or thereabouts, no spiking on data registered every few minutes. Humidity was high, some cloud, lot of turbidity. (sticky hot day, not nice)
Met Office station Boscombe Down more or less matches both and is sensibly located as a check.
LWIR outgoing is limited by water again.
Turning to night minima, unlike Heathrow the night before Hurn does read correctly, agreeing with Chilbolton. Slight wind at Hurn was from the north running over grass.
Weather is forecast to be warmer maybe Wednesday and Thursday (when Scotland will turn hot).
I wasn’t intending following the stations, oh well, have real science to do, some fun on the way, appear here first.
Note: published with the wrong date to avoid “covering” other blog posts.
Tim
Tallbloke's Talkshop 
Sounds similar to Sydney when it had its highest temp back in Jan, 2013. The station was recording the temp every 10 mins. Somehow it rose nearly a degree and then dropped a degree in the space of 10 mins.
44.9C to 45.8C and back to 44.7C – all in ten mins. Go figure.
No surprise but why exactly needs more information, both boring and interesting. Do any of these organisations employ metrologists? (spelt correctly)
A beauty appeared yesterday, temperature abruptly rose early evening at Chivenor, horrible site. Wind was unstable, swung around to north for an hour or so, https://tallbloke.wordpress.com/2012/09/10/wmo03707-chivenor/ (locals apparently complain about this site when it is referred to from on high)
Sure this is hot weather but details are making a mess, plus a few horrors. The Met Office know this, or at least errors are plain to see in their published data. For example, a general temperature irregularity except centred on sites… which is a site problem. And they do nothing whatsoever about it.
Having seen life from the sharp end there is no mystery.
Aside: the Chilbolton data is now semi-useless, radiation data ceased. Sadly from our point of view learning more about rare weather conditions is lost, instruments have been removed for service and calibration. (apart from a clean, there is nothing to adjust, I know that, they won’t know, not very accurate anyway, weeks or months)