Portugal is defined as a Mediterranean climate (Csa in the South, interior, and Douro region; Csb in the North, Central Portugal and coastal Alentejo; mixed oceanic climate along the northern half of the coastline and also Semi-arid climate or Steppe climate (BSk in certain parts of Beja district far South) according to the Köppen-Geiger Climate Classification), and is one of the warmest European countries: the annual average temperature in mainland Portugal varies from 8–12 °C (46.4–53.6 °F) in the mountainous interior north to 16–19 °C (60.8–66.2 °F) in the south and on the Guadiana river basin. The Algarve, separated from the Alentejo region by mountains reaching up to 900 metres (3,000 ft) in Alto de Fóia, has a climate similar to that of the southern coastal areas of Spain or Southwest Australia.
In the south of Portugal and on the Guadiana river basin, between what degrees does the average temperature fluctuate?
16–19 °C (60.8–66.2 °F)