The climate varies from subtropical and dry in central and eastern Azerbaijan to subtropical and humid in the southeast (Lankaran Lowlands), moderate along the shores of the Caspian Sea, and cold at the higher mountain elevations. In Baku, the climate is cool in the winter, averaging 4 degrees C (39F) in January. Summers are hot, up to 40 degrees C (104F), and humid because of the sea. There are often strong winds, especially during winter. Snow rarely settles in the city. Spring and autumn are pleasant and there is a great deal of sunshine from April to October.
Because most of Azerbaijan receives scant rainfall—on average 152 to 254 millimeters (5.9 to 10 inches)— annually, agricultural areas require irrigation. The heaviest precipitation occurs in the highest elevations of the Caucasus and in the Lankaran Lowlands in the far southeast, where the yearly average exceeds 1,000 millimeters (39 inches).