The Augusts of the 1920s were generally poor months and at times particularly cool, whilst the Augusts of the 1930s tended to be warmer with notable heatwaves

1920s decadal August average: 15.0C
1930s decadal August average: 16.3C

Number of days with a daily CET mean of 20.0C+

1920s: 1
1930s: 17

There was only one August in the 1920s that breeched the 16.0 CET mark: (1926: 16.2)
There were 7 August in the 1930s that breeched the 16.0 CET mark and 2 that breeched the 17.0 CET mark (1932: 17.1; 1933: 17.6)

The Augusts of the 1930s tended to be drier as well

1920s August rainfall average: 89.9mm
1930s August rainfall average: 65.9mm

There were no sub 50mm Augusts in the 1920s, there were 4 in the 1930s.

Kew Gardens sunshine averages

Augusts of 1920s: 174.2hrs

Augusts of 1930s: 191.4hrs

The summer of 1921 was exceptionally dry and hot until the August, which was a real cuckoo in the nest. It was the 2nd wettest month of that very dry year. 

In the summer of 1976 I was a student working on a farm in Suffolk. The farm owner, who was retired, had reference years for every weather extreme such that anything you said about the weather could be met with a shake of the head and a comment "Well, of course in 19XX it was colder/wetter/hotter etc. etc." It was a standing joke that he had experience to quote which surpassed any moan we could make about current conditions.

His reference year for hot summers was 1921 (as it was for many other elderly farmers back then) so as 1976 progressed, no matter how bad things got (physical labour was no fun in such heat), there were endless comparisons as to how much worse 1921 was. By the end of the summer, though, he very reluctantly conceded that perhaps 1921 was not quite as severe.

I see there's this:

https://www.theguardian.com/news/2011/oct/13/weatherwatch-drought-margate-eliot-waste-land

and the preview section of this:

https://www.jstor.org/stable/4118615?seq=1#page_scan_tab_contents