> my personal ideal weather _is_ cool/gray/wet with ideal outside temperature of 15C
15C day temps? morning/night temps can be much lower. Winters in Norway are much colder. If you are looking for stable day-night temps year around in that range, then there is no such place in Europe, well maybe except Ireland?
June-Sept in most places in Ireland has a mean daily temp of around 15C, and around 6C winter time. It infrequently gets much above 20C, or much below 0C year round. 5 consecutive days of 25C is the meteorological definition of "heatwave".
As a predominantly temperate maritime/oceanic climate it's unpredictable and erratic, from 15C mid-winter days to 4C mid-summer nights :/
15C day temps? morning/night temps can be much lower. Winters in Norway are much colder. If you are looking for stable day-night temps year around in that range, then there is no such place in Europe, well maybe except Ireland?