The climate of Santander is oceanic (Köppen climate classification Cfb), the annual thermal oscillation of the average monthly temperatures reaching around 10 °C.
The humidity is quite high throughout the year and sometimes reaches more than 90%. Average daily maximum temperatures vary from 23 °C in summer down to 13 °C in winter.
The maximum temperature reached in Santander was 37.4 °C on 31 August 2009 and the minimum temperature −5.4 ° C on 21 January 1957