Temperatures vary widely from one geographical zone to another, and frequently within zones, depending on the altitude. In the lowlands, temperatures reach 32°c (90°f) or more in the summer and rarely fall below -7°c (19°f) in the winter. The range in the highlands is greater; temperatures sometimes fall below -18°c (0°f), and frost and hail are frequent hazards. Rainfall, which is mostly concentrated in the months from October to April, averages 71 cm (28 in) annually, varying from 191 cm (75 in) in parts of the mountains to as little as 60 cm (24 in) in the lowlands. Most of the rainwater is lost through runoff, and droughts are common.