It's looking like a 12.9 for May to me at the moment. I've just been looking at some similar years and found this close one in 1911 and here it is starting from January:
3.8, 4.8, 5.2, 7.5, 12.9, 14.5, 18.2
2016
5.4, 4.9, 5.8, 7.5, (12.9)p
Interestingly 1911 had a Summer which finished in the Top Ten of all time