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  in some parts of the coast (according to the Portuguese Meteorological Institute). Some islands in Azores do have drier months in the summer. Consequently, the islands 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 Humid subtropical (''Cfa''), transitioning into an Oceanic climate (''Cfb'') at higher altitudes, according to Köppen-Geiger classification.