Here's a Times report on the heatwave of late August 1930. Up to the last few days of that month, August 1930 had been fairly cool to average. The heatwave kicked in on the 26th.
28th August: 33.9C
29th August: 34.4C
Record maxima for these dates.
33.3C on the 28th at Cambridge
33.9C at Norwich on the 29th
32.2C at Nottingham on the 29th
Temperatures of 26.7C+ were recorded generally from southern Scotland, southwards on the 27th.
The CET for the month ended as 15.7
Kew Observatory maxima
24th: 20C
25th: 22.2C
26th: 28.9C
27th: 28.9C
Minimum
30th: 19.4C
Eskdalemuir
26th: 17.8C
27th: 28.3C
At 5000ft over Duxford, the temperature was 21.7C on the 27th.
A front moving eastwards brought severe thunderstorms. There was a steep lapse rate above 7000ft with moisture in the lower layers according to reports at the time.
MANCHESTER SUMMER INDEX for 2021: 238
Timelapses, old weather forecasts and natural phenomena videos can be seen on this site
http://www.youtube.com/channel/UCgrSD1BwFz2feWDTydhpEhQ/playlists