"Nick G" wrote in
:

According to my weather book, 30C occurred on the 16th of April 1949
in London.
snip

Yes, but that's (I assume) the earliest date on which 30°C *was* reached.
My point was whether 13th June was the latest date on which is has *not*
(ever) been reached.

--
Bewdley, Worcs. ~90m asl.