Funny thing is that it is currently (only?) 18.0ºC in my garden but it feels perfectly pleasant. I guess it's now time for Pimm's and tennis.

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Well you're beating me Doc, only 17.1C here.

Heathrow hit 28C at 1300. Just 0.1 C of this year's maximum so far...

...while Hurn reported 28.5°C at the same time

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Just cracked 30.0c here in the unbroken sunshine.

Not quite... Hurn is 28.5 at 1400 (making it the warmest temperature of the year do far), but was only 27.7 at 1300 (at which time Heathrow was the hottest at 28.0).

28.5C.
Some cumulus has developed, but nothing significant.

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26.7'C here, easily the warmest of the year. Unbroken sun and actually feels like summer

A beautiful day. The frontal cloud is providing some welcome shade from time to time.

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For some strange reason it actually feels warmer on the coast than it did when I visited a friend who lives a couple of miles inland, its roasting hot at the front of my west-facing house under unbroken sunshine (if somewhat on the hazy side). Even the pavement is too hot to stand on barefoot for too long!

I am recording 24.5 C which is very respectable for my coastal location. Amazing to think that it was this time last week I was shivering and had an electric heater on for mother as mist and low cloud rolled in from the sea and kept temperatures pegged around 15 C.

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At 1500 Heathrow has the hottest hourly max. 28.8C

According to the observations page on the Met Office, Heathrow has been up to 29.2c too.

28.8 C was hottest hourly I could find?

http://www.metoffice.gov.uk/weather/uk/observations/ 
http://www.metoffice.gov.uk/public/weather/observations/heathrow#?tab=last24hours&fcTime=1373065200 

Is there another link you have?

http://www.metoffice.gov.uk/public/weather/observations/heathrow#?tab=last24hours&fcTime=1373065200  Is there another link you have?