The contours of the Garraf region determine the special climatology of the area. The Garraf massif is located in the middle of two zones: the Baix Llobregat and the Garraf. Castelldefels and Gavà are on the north side and Sitges and Vilanova on the south. In the same massif the Litoral range of hills also rises, which slopes down to the coast at Castelldefels. For this reason, temperatures in the Baix Llobregat are higher and the summers more sultry. Since the Litoral range is lower at this point, neither Castelldefels nor Gavà enjoy the fresh breezes blowing down from the hills. Both Sitges and Vilanova, however, are backed by hilltops. Furthermore, far less heat is given off in the Garraf region than in the Baix Llobregat and Barcelona areas, and there is less industrial development.



That is why the climate in and around Vilanova i la Geltú is relatively mild, characterized by cool winters and warm summers, when the heat is moderated by the sea, the Garraf massif and the Litoral range of hills, giving an average annual temperature of 16.1º C. The coldest month is January, with an average of 10º C, and the warmest is August, with an average of 24º C.



As for rainfall, the annual average is 540 mm, distributed in an irregular way, except for a recurring dry season, both throughout the year and from year to year. The months with most rainfall are September and October, and those with least July and February.