My guess is that
@ninnymary has a similar climate to yours, Marie.
However, she is so close to California's Central Valley that it is probably surprising to her and her neighbors that it's so much cooler during Bay Area summers. Just across that valley are the very high Sierra Nevada mountains and their alpine weather.
I know that the UK has mountains but I wonder about deserts and semi-arid regions.
When it was 36°c, the humidity was 10% and the dew point was 0°c. In other words, the would have to be frozen to squeeze any moisture out of it. So, the dry air cannot "blanket" the land with moisture and, overnight, the temperature plunges.
This jumping up and down in temperatures is common but this is a bit extreme! I looked at some nearby communities: Wallace Idaho is in the mountains and close to the Montana border, 34°c (93°f) after a morning of 6°c (42°f). Deer Park Washington isn't in the mountains and it was 34°c (93°f) after a morning of 7°c (44°f).
Steve