Interesting point Bert - also made by Jiries above too
Devilishly difficult to know one way or the other
I have daily max data for my nearest site (Kew Gardens) and these show the opposite so maybe there is a location dimension too
At Kew Gardens the maxima for JJA are 34.8 (26/06/1976), 37.6(25/07/2019) and 37.9 (10/08/2003)
I see that it doesn't apply in Kew- and as Jiries said, there's no modifying aspect of water in the Canadian record, and Kew is (a bit) more like that ;it's more remote from the sea than the S Coast. I suppose if all other factors were in line with conditions in July/August, include high upper temps and thicknesses, sort of level ground starting block, and the only remaining one was solar angle, then it would make a difference. How did Kew do on 1st July 2015, can you remember? Conditions were pretty good then, with 20+ 850s I think, although 2019 clearly pipped it.
Bertie, Itchen Valley.
Definition of disappointment: brown birch bolete