The dense river network that drains the republic includes two large swift rivers, the upper courses of the Syr Darya and the Amu Darya , together with their tributaries, notably the Vakhsh and Kofarnihon . The Amu Darya is formed by the confluence of the Panj and Vakhsh rivers; the Panj forms much of the republic’s southern boundary. Most of the rivers flow east to west and eventually drain into the Aral Sea basin. The rivers have two high-water periods each year: in the spring, when rains fall and mountain snows melt, and in the summer, when the glaciers begin to melt. The summer flow is particularly helpful for irrigation purposes.

The climate of Tajikistan is sharply continental and changes with altitude. In the warm-temperate valley areas, summers are hot and dry; the mean temperature in July is 81 °F (27 °C) in Khujand (Khojand) and 86 °F (30 °C) in Kŭlob (Kulyab), farther south. The corresponding January figures are 30 °F (−1 °C) and 36 °F (2 °C), respectively. In very cold winters, temperatures of −4 °F (−20 °C) and lower have been recorded. Annual precipitation is slight and ranges between 6 and 10 inches (150 and 250 millimetres) but is higher in the Gissar Valley. In the highlands conditions are different: the mean January temperature for Murghob in the Pamirs is −3 °F (−20 °C), and temperatures can drop to −51 °F (−46 °C). In this area precipitation barely reaches 2 to 3 inches a year, most of it falling in summer. Moist air masses move from the west up the valleys, suddenly reaching low-temperature areas and producing locally heavy precipitation, mainly heavy snow of as much as 30 to 60 inches of annual accumulation.

The topographic and climatic variety gives Tajikistan an extremely varied plant life, with more than 5,000 kinds of flowers alone. Generally grasses, bushes, and shrubs predominate. The country’s animal life is abundant and diverse and includes species such as the great gray lizard, jerboa, and gopher in the deserts and deer, tiger, jackal, and wildcat in wooded areas or reedy thickets. Brown bears live at lower mountain levels, and goats and golden eagles higher up.