Other factors, too, such as the traditional forms of land tenure, have varied in the different regions. In the 1980s their degrees of separation were still sufficiently pronounced to represent a significant obstacle to efforts toward achieving a fully unified Libya. Area: "Total:" 1 759 540 km² "Land:" 1 759 540 km² "Water:" 0 km²  Area - comparative: Libya is the fourth largest country in Africa, seven times the size of the United Kingdom, and slightly larger than Alaska. Land boundaries: "Total:" 4 348 km "Border countries:" Algeria 982 km, Chad 1,055 km, Egypt 1,115 km, Niger 354 km, Sudan 383 km, Tunisia 459 km  Coastline: 1,770 km  Maritime claims: "Territorial sea:"  "note:" Gulf of Sidra closing line – 32 degrees, 30 minutes north. "Exclusive economic zone:"  Within Libya as many as five different climatic zones have been recognized, but the dominant climates are the hot-summer Mediterranean climate and the hot desert climate (Köppen climate classification "Csa" and "BWh"). In most of the coastal lowland, the climate is Mediterranean, with hot or very hot summers and extremely mild winters. Rainfall is scant. The weather is cooler in the highlands, and frosts occur at maximum elevations. In the desert interior, despite the relatively high elevation, the climate has long, extremely hot summers and high diurnal temperature ranges due to the permanence of cloudless skies and excessively dry atmosphere. The highest official temperature ever recorded was on 13 September 1922 at 'Aziziya, Libya, but that reading is queried. Less than 2% of the national territory receives enough rainfall for settled agriculture, the heaviest precipitation occurring in the Jabal al Akhdar zone of Cyrenaica, where annual rainfall of is recorded. All other areas of the country receive less than , and in the Sahara Desert or less occurs. Rainfall is often erratic, and a pronounced drought may extend over two seasons. For example, epic floods in 1945 left Tripoli underwater for several days, but two years later an unprecedentedly severe drought caused the loss of thousands of head of cattle. Deficiency in rainfall is reflected in an absence of permanent rivers or streams, and the approximately twenty perennial lakes are brackish or salty. In 1987 these circumstances severely limited the country's agricultural potential as a basis for the sound and varied economy Gaddafi sought to establish.