If you're looking at mean temperature then 2003 had the highest here followed by 1933 and 1976.
I don't think this is a suitable indicator of heat as this includes night temperatures which are irrelevant and are higher now due to increased urbanisation and increases in unpleasant humid, muggy and cloudy airmasses.
Looking just at day temperatures then 1976 is the winner here followed by 1933 and 2003. Surprising that 2003 just pipped 1995 into third place but the early part of June was very poor with a max of 9C on the 7th. The warmth in 2003 was more consistent but never as exceptional.
Here are the five summers with the highest mean max at Dyce:
1976: 20.0C
2003: 19.3C
1995: 19.1C
2006: 19.0C
1975/2018: 18.9C
No station existed there in 1933 but Craibstone, which is higher altitude and less sheltered, recorded 19.1C. Comparisons with the other summers suggest about 0.5C difference so this would place 1933 in clear second.
1911 and possibly 1901 too may well have beaten 2018. I'm not sure at the moment but trying to construct a standardised temperature series back to the 19th century from all the various stations that have existed in the area.
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