winter and 10–12 h in the summer, with higher values in the southeast and lower in the northwest.
The sea surface temperature on the west coast of mainland Portugal varies from 13 °C (55.4 °F)-15 °C (59.0 °F) in winter to 18 °C (64.4 °F)-20 °C (68.0 °F) in the summer while on the south coast it ranges from 15 °C (59.0 °F) in Winter and rises in the summer to about 23 °C (73.4 °F) occasionally reaching 26 °C (78.8 °F).
Both the archipelagos of the Azores and Madeira have a subtropical climate, although variations between islands exist, making weather predictions very difficult (owing to rough topography). The Madeira and Azorean archipelagos have a narrower temperature range, with annual average temperatures exceeding 20 °C (68 °F) along the coast (according to the Portuguese Meteorological Institute). Some islands in Azores do have drier months in the summer. Consequently, the island of the Azores have been identified as having a Mediterranean climate (both Csa and Csb types), while some islands (such as Flores or Corvo) are classified as Maritime Temperate (Cfb) or Humid subtropical (Cfa), respectively, according to Koppen-Geiger classification. Porto Santo island in Madeira has a semi-arid Steppe climate (BSh). The Savage Islands, which are part of the regional territory of Madeira are unique in being classified as a Desert climates (BWh) with an annual average rainfall of approximately 150 mm (5.9 in). The sea surface temperature in the archipelagos varies from 17 °C (62.6 °F)-18 °C (64.4 °F) in winter to 24 °C (75.2 °F)-25 °C (77.0 °F) in the summer occasionally reaching 26 °C (78.8 °F)
