La Coruna possibly has the coolest summertime temperatures in Spain though the effect of the sea, and possibly the cloud cover, result in winter temperatures as good as the balearic islands.
This corner of Spain is rugged with much of the land being over 500m above sea level causing local variations in the weather.
La Coruna is on the wettest corner of Spain with the average rainfall being 998mm or 39.8 inches (Source: World Climate), and although most falls from October to April, there will be a chance of rain in any month.
Daily average temperatures for La Coruna
Source: World Climate