Roger J Smith - Further to your analysis of Summers following warm May's. Could you do this with regards to years 1998 & 2008? Both had rubbish summers after warm and sunny May's. Indeed seems to be a bit of a curse for years ending in 8 when you throw in 1978 and 1918.
My own analysis of this has looked at all the years since 1900 (dont trust the pre 20th century warm figures) with 13+ CET for May and throwing in one exception. They are as follows: 1918, 1919, 1947, 1952, 1964, 1970, 1989,1992, 1998, 2008. I would also like to throw in 1911 which had a May CET of 12.9
Of these the Summer that follows is a bit of a mixed bag but three patterns seem to emerge. Either 1. The summer that follows is abysmal (eg. 1919, 1964, and all the years ending in an 8 OR 2. The summer continues into an exceptional June then crashes in July August (1970, 1992) OR 3. The summer is a true record breaker (1947, 1989 and 1911).
We shall see what follows this year but I think its all noticeable that many of the exceptional summers (17+ CET across the summer) of the 20th century did have above average Mays. Really only 1983 goes against this.