The principal features of Australia’s climate stem from its position, shape, and size. Australia is mainly a compact tropical and near-tropical continent. No major arms or embayments of the sea penetrate far into the landmass. The only extensive uplands occur near the east coast, and even they are not, by world standards, very high. In summer (December–February), when the sun is directly overhead in northern Australia, temperatures are extremely high. The sea exerts little moderating influence, and the uplands are not sufficiently extensive or high to have more than local effects. Temperatures commonly soar above the 100 °F (38 °C) mark in the interior, but because there rarely is any cloud cover, radiation loss is considerable at night, and daily temperature ranges are wide. High temperatures dominate the Australian summers in all but Tasmania.

Heat waves are common, and, though the highest amounts of solar radiation are received in northern South Australia, the highest temperatures and longest heat waves are recorded in the northwest of Western Australia. For example, Marble Bar has recorded a maximum temperature of 100 °F or more on 162 consecutive days. Temperatures in winter remain moderate except in the uplands of Tasmania and southeastern Australia, where snow is common. Night frosts are common in winter throughout southern Australia and in the interior. Because of its relatively low latitudinal position, Australia comes under the influence of the southeast trade winds in the north and the westerlies in the south. Northern Australia is affected by a northerly monsoon, partly because of the latitude and the seasonal migration of planetary wind zones and partly because of the summer heating of the continental interior that draws in surface winds. The monsoon brings summer (December–February) rains to the northern coastal area that penetrate inland for variable distances. These summer rains are all the more important because most of northern Australia is in the sheltered rain shadow of the Eastern Uplands, which block the rain-bearing southeast trades in winter. The trades, forced to rise by the uplands, bring heavy rains to the Pacific coasts of Queensland and northern New South Wales. These areas are also affected by tropical cyclones and receive the heaviest rains of any part of Australia. Within this coastal fringe, the northern Queensland area around Tully, south of Cairns, is the wettest, with an annual average of nearly 160 inches (4,050 mm).