[4] According to the European Environment Agency, Bilbao lies within the Atlantic biogeographical region.
[5] The climate of Bilbao and the rest of the north-western part of Spain (the so-called Green Spain) is different from the rest of the country, characterized by a higher amount of rainfall and precipitation days, fewer sunshine hours and mild temperatures, in summer comparable to northern half of Europe with temperate climate.
Said proximity to the ocean also makes that the two most defined seasons (summer and winter) remain mild, with low intensity thermal oscillations.
[7] Average relative humidity is 72%, ranging from 70% in February and March to 74% in August and November.
[6] This is similar result (range of 1,200-2,000 hours) which is recorded in the northern half of Europe, for example: London, Warsaw; but in winter Bilbao has about two times more sun duration than in the northern half of Europe.
In the month of August 2003, the average reported daytime maximum temperature was a record 29.9 °C.