Utah drainage areas may be divided into three sections. The northwestern corner of the State drains through the Raft River country into the Snake River. The remaining drainage is divided between the Great Basin and the Colorado River system. Large areas in eastern Utah, together with most of the southern plateaus, drain through the Green River and other tributaries into the Colorado. Largest of these tributaries are the Fremont, San Juan, and Virgin rivers. Some streams, however, flow from eastern Utah or from the plateaus into the Great Basin. The most important stream flowing through the northeastern part of the State is Bear River, which originates on the north slope of the Uinta Mountains in Utah, flows across a corner of Wyoming, back into Utah, then loops into Wyoming and Idaho before discharging its waters into Great Salt Lake. Many streams cut through the Wasatch Mountains to find their way into Utah Lake or Great Salt Lake. Among these are the Weber, Ogden, Provo, and Spanish Fork rivers. The Sevier River flows out of the Panguitch Plateau, and disappears into the Sevier Desert, and the few small streams rising in the western ranges run dry before they have progressed far across the floor of the Great Basin.
An average elevation of approximately one mile above sea level is the principal factor in determining Utah's temperate climate. The Santa Clara Valley and the Virgin River Valley, with an elevation of 2,700 feet, are known as Utah's Dixie. Their winters are comparatively free from storm, and they have a semi-tropical climate and a warm dry atmosphere. In mountainous regions of the State the temperature is low in the winter and moderate in the summer. In the higher reaches of the Wasatch and Uinta mountains, particularly, the summers are short and the winters cold and long. The lowlands adjacent to the mountains have a pleasant temperate climate, with only a few extremely hot or cold days. Temperatures in Salt Lake City occasionally reach 100 degrees in midsummer and sometimes fall to 10 degrees below zero in winter.
Precipitation also is largely determined by the altitude. The high mountain ranges receive as much as forty inches per year, most of which comes in the form of snow; the valleys near the mountains receive about fifteen inches; and the desert regions are fortunate if they get as much as five inches. The Wasatch Mountains are responsible for much of the precipitation on the arable land of the State. Rain-bearing clouds from the Pacific Ocean cross the hot deserts of the Great Basin, and when they strike the cool mountain air, rain or snow falls upon the western slopes of the Wasatch Range. Because of the precipitation in this section, a great agricultural belt paralleling the mountains has been developed.