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 :/

Plenty of grey and wet though.