to the topography of the state. Summers in Wyoming are warm with July high temperatures averaging between in most of the state. With increasing elevation, however, this average drops rapidly with locations above averaging around . Summer nights throughout the state are characterized by a rapid cooldown with even the hottest locations averaging in the range at night. In most of the state, most of the precipitation tends to fall in the late spring and early summer. Winters are cold, but are variable with periods of sometimes extreme cold interspersed between generally mild periods, with Chinook winds providing unusually warm temperatures in some locations. Wyoming is a dry state with much of the land receiving less than of rainfall per year. Precipitation depends on elevation with lower areas in the Big Horn Basin averaging , making the area nearly a true desert. The lower areas in the North and on the eastern plains typically average around , making the climate there semi-arid. Some mountain areas do receive a good amount of precipitation, or more, much of it as snow, sometimes or more annually. The state's highest recorded temperature is at Basin on July 12, 1900, and the lowest recorded temperature is at Riverside on February 9, 1933. The number of thunderstorm days varies across the state with the southeastern plains of the state having the most days of thunderstorm activity. Thunderstorm activity in the state is highest during the late spring and early summer. The southeastern corner of the state is the most vulnerable part of the state to tornado activity. Moving away from that point and westwards, the incidence of tornadoes drops dramatically with the west part of the state showing little vulnerability. Tornadoes, where they occur, tend to be small and brief, unlike some of those that occur farther east. Location and size As specified in the designating legislation for the Territory of Wyoming, Wyoming's borders are lines of latitude 41°N and 45°N, and longitude 104°3'W and 111°3'W (27 and 34 west of the Washington Meridian)—a geodesic quadrangle. Wyoming is one of only three states (the others being Colorado and Utah) to have borders defined by only "straight" lines. Due to surveying inaccuracies during the 19th century, Wyoming's legal border deviates from the true latitude and longitude lines by up to half of a mile (0.8 km) in some spots, especially in the mountainous region along the 45th