Bilbao is close to the Bay of Biscay which gives it an oceanic climate. This means that, apart from a well defined dry summer season, it can rain all year round with the wettest part of the year being October to April.
It doesn’t snow often in the city but snow can be seen on the surrounding mountains and it is known to sleet for approximately 10 days of the year.
Both the summer and the winter seasons are mild due to the proximity to the sea with average temperatures ranging between 25 °C (77.0 °F) and 26 °C(78.8 °F) in the summer months, while the average minimum in winter is between 6 °C (42.8 °F) and 7 °C (44.6 °F).
The highest and lowest recorded temperatures in Bilbao are 42.2 °C (108.0 °F) maximum (on 13 August 2003) and −8.6 °C (16.5 °F) minimum (on 3 February 1963). The maximum precipitation in a day was 225.6 mm (9 in) in 26 August 1983 when severe flooding was originated by the Nervión river.
To keep up to date with the weather in Bilbao look HERE