i'm not saying there's any causality. it's just a correlation. it could be random, but statistically that's very unlikely, to keep getting a very hot summer every 11th year. the solar cycle is 11 years, so maybe there's some causality there, but very difficult to prove the precise mechanism.
come to think of it, i think the summer of 1933 was also very hot. so this correlation goes back a very long time.