Although it has a wide diversity of climatic conditions, Australia is generally warm and dry, with no extreme cold and little frost, its temperatures ranging from comfortably mild in the south to hot in the central interior and north. July mean temperatures average 9° C (48° F ) in Melbourne in the southeast and 25° C (77° F ) in Darwin in the north. January mean temperatures average 20° C (68° F ) in Melbourne and 30° C (86° F ) in Darwin. Summer readings often reach 38° C (100° F ) or more in almost any area of the continent and may exceed 46° C (115° F ) in interior regions. Winds are light to moderate, except along the coasts, where cyclones have occurred.
The continent is subject to great variations in rainfall, but except for a few areas rainfall is insufficient, and the rate of evaporation is high. Mean annual rainfall is 42 cm (17 in), much less than the world mean of 66 cm (26 in). About 18% of the land area is desert. Only about 20% has more than 76 cm (30 in) of rain annually, but these areas suffer from a long dry season, while others have too much rain. Only Tasmania, Victoria, and parts of New South Wales have enough rainfall all year round. Droughts and floods occur irregularly but frequently over large areas. On 25 December 1974, a cyclone and flood devastated most of Darwin; at least 49 people were killed, and some 20,000 were left homeless. Drought conditions became very severe in the early 1980s, leading to dust storms, fires, and multibillion-dollar crop losses. Again in 1994–95, a severe drought devastated eastern agricultural regions.