Northern Australia - Geography and Climate

Geography and Climate

Almost all of Northern Australia is a huge ancient craton that has not experienced geological upheaval since the end of the Precambrian. the only exception to this generalisation is the Wet Tropics of northern Queensland, where active volcanoes have been present as recently as the Pleistocene.

The vast craton in the north and west contains a number of quite rugged mountain ranges, of which the highest are the MacDonnell and Musgrave Ranges on the southern border of the Northern Territory. These rise to over 1,500 metres (4,900 ft), but the most spectacular features are the deep gorges of rivers such as the Finke. Most of the craton, however, is distinctly flat and generally low-lying with an average elevation of around 400 metres (1,300 ft), whilst in the Lake Eyre Basin most of the land is not far above sea level.

The climate of the north of Australia ranges from arid (Köppen BWh) in the south to monsoonal (Köppen Aw) in the Top End and Kimberley. On the eastern coast, however, the climate is much more humid and ranges from humid sub-tropical (Köppen Cfa around Brisbane and Cwa further north) to humid tropical (Köppen Am and Af) in the Wet Tropics. Except in the western part of the Pilbara and Gascoyne where the heaviest rain often occurs from May to July under northwest cloudbands, rainfall is heavily concentrated in the "summer" months from November to March. For instance, in Burketown, the months May to September are rainless in over fifty percent of years, with over eighty percent of Augusts having no rain.

Temperatures in summer are generally unpleasantly hot apart from the eastern coastal belt. Maximum temperatures elsewhere between October and April range from 30 °C (86 °F) in the south in April to around 40 °C (104 °F) in the inland Pilbara and Kimberley before the wet season breaks. Further north, maxima are consistently around 32 °C (90 °F) but extreme humidity makes conditions very unpleasant. On the coast, maxima in January range from 29 °C (84 °F) in the south to 32 °C (90 °F), with minima generally around 21 °C (70 °F).

In July, temperatures show a wider range, from 31 °C (88 °F) in the north to around 19 °C (66 °F) in the south, where minima can be as low as 5 °C (41 °F) in Alice Springs in June and July.