Pakistan consists largely of high mountains, plateaus, and lowland plains. Its mountainous section, occupying about half of the land, lies west of the Indus River. Beginning near the Arabian Sea, ranges extend northeastward and increase in height toward the Himalayas. Peaks rise more than 11,000 feet (3,350 m) above sea level in the Sulaiman and other central ranges. In the majestic Hindu Kush range of the far north stands glacier-capped Tirich Mir. Rising to a height of 25,230 feet (7,690 m), it is the highest peak in Pakistan. Breaching the ranges are many passes, most notable of which is Khyber Pass. The largest plateau area lies in Baluchistan, in the southwest.
Lowlands prevail east of the Indus River. In the Punjab region, in the northeast, fertile alluvial plains parallel the rivers. There is also some steppe and arid land, notably the That Desert. Most of the Sind region in southeastern Pakistan fringes the Thar, or Great Indian, Desert—a virtual wasteland except in areas where irrigation water is available.
Pakistan is drained primarily by the Indus River and such principal tributaries as the Jhelum, Chenab, Ravi, and Sutlej rivers. The Indus system is extremely important to both India and Pakistan. In many areas, irrigation water supplied by the rivers is the only means of sustaining life. The Indus Waters Treaty of 1960, negotiated through the World Bank, allocates the waters of the Indus, Jhelum, and Chenab to Pakistan and the waters of the Ravi and Sutlej to India. Hydroelectric power, flood control, and irrigation water are provided by several large dams, chief of which are the Tarbela, on the Indus, and the Mangla, on the Jhelum. By volume, the Tarbela dam is the world's largest.
Except in mountainous areas, where the climate is determined largely by elevation, Pakistan has a subtropical climate that is extremely hot and dry.
Beginning in February, after a brief cool period, temperatures rise rapidly. Well before June (the hottest month), daytime highs of 110° to 120° F. (43° to 49° C.) occur throughout most of the land. Nights bring only slight relief from the intense heat. Virtually no rain falls during this time.
Late June or early July usually marks the beginning of the southwest monsoon, which lasts until September and brings almost all the rain received each year. It also brings a cloud cover that slightly reduces the heat. Except in parts of the north, where 20 to 40 inches (500 to 1,000 mm) may fall, precipitation is scant. Less than 10 inches (250 mm) a year is normal for most of the country. Large areas receive less than 5 inches (125 mm).
October through January is the cool season. It is dominated by the northeast monsoon, which brings cool air from the interior of Asia. Average January temperatures range from about 50° F. (10° C.) on the northern plains to more than 65° F. (18° C.) in the south. Temperatures below freezing are relatively rare and occur only in the north. Only the high mountains receive snow.