Actually August will in all probability be just fine. The biggest 'deal' is most likely to be lack of wind.
Last year's spring was just as crappy as this, maybe not so cold, but wetter.... come July 1st somebody threw a switch... I think we had 2 or 3 days of cloud/showers between then and September.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)