There was a very notable heatwave during mid July 1868 where maximum got into the 90+Fs including a temperature recording of 100.5F at Tonbridge on the 22nd of July 1868. However, this figure is now discredited as the temperature was not recorded at standard exposure.

15th-22nd July 1868 CET: 20.6C

Overall CET: 18.3C

Here is a selection of some other temperatures recorded during that period although the readings are questionable as to whether they are what we would call "standard exposure"

Camden Town: Only 1 day on which shade max. was below 72F, on 4 days it was above 90F

Linton Park: An exceedingly hot and dry month. Water becoming scarce

Hitchin: Such heat, such drought and such a high barometer have never been recorded during 19 years, the barometer has been below 30 inches only on 17 days out of the last 92.

Culford: Shade max of 90F and upwards on 4 days. Wheat crop excellet but turmips and green crops and entire .

Cirencester: An extraordinary month for heat, yet breezt and cool nights; the intense sun and cloudless sky account for burnt pastures.

Shifnal: Another broiling month.

Orleton: A remarkably brilliant hot and dry month.

Boston: A month of unusually high temperatures; cloudless skies and amost no rain. Pastures burnt and bare and great hardships both for man and beast owing to the want of wate rin the Fen Districts.

Cefnfaes: Hot and dry, water very scarce in this district.

Dumfries: Hot and droughty, water very scarce in the district.

Auchendrane: River Doon normally 104ft wide is reduced to a stream of just 6ft wide and 2ft deep.

Ballater: The river Dee lower than ever observed.

Aberdeen: Remarkable for heat and drought, pastures burnt up.

Doo Castle: Intense heat and great drought, spring wells dried up.

Although 1868 was a good summer overall, it wasn't really that exceptional, being ranked only 14th out of the CET series from 1659.

Still, it is the first in the CET summer series that ends with an '8', so this tends to underline the theory that good summers ending in '8' are few and far between!

Let's hope 2018 redresses the balance and comes up with a summer better than 1868, which stands in the CET summer series at 16.87C.

Have to take into consideration there was a very warm May and May-July was exceptionally dry,  that period was actually drier than the summer of 1976 by a touch for England and Wales. 

Almost like this year.

This year's summer has got off to a cracking start. Although I don't think we'll end up overall hotter than 1976 - however, the mechansim is in place to record more sunshine as June has been so good.

June 1976 didn't really get going until the 20th. Indeed in the first 10 days of June 1976 there were ground frosts in places.

I agree. From memory, this June has been far more pleasant overall compared to June 1976. This month has had plenty of sunshine, but not overbearingly hot, just very nice indeed. 

As you say the last ten days of June 1976 made all the difference. It was ridiculously hot, certainly in central London where at the time it was just downright uncomfortable. Apart from the high temperatures it also felt very humid. That hot spell then continued into July that year. The rest is history.

What is so interesting this year for me is the possible continued presence of high pressure well into July. If this continues it will mean a hot month, but how hot will depend on the position of the high, and whether it sucks up heat from the near continent?

Either way, we are in a fascinating situation. If July comes out well above average, and August continues in the same vein, we could end up in the top five summers in the CET series. Intriguing stuff!

A couple of thoughts about those fascinating figures for 22nd July 1868. That the Tonbridge figure is unreliable is strongly indicated by the value for Tunbridge Wells, only a mile or two away, being only 92.4F (if I've remembered the tenths of a degree correctly). Even so, it was clearly an exceptionally hot day. The effect of what was probably a sea breeze at the coastal stations Ventnor, Worthing and Sidmouth shows up well, keeping maxima there some 10F cooler.