Australia is the driest habitable continent on earth, and as a continent is subject to many different weather areas. The arid zone covers over 70% of the inland and is made up of many microclimates. Climatologists agree that the arid zone is set by isohyets ( the contours of areas of equal rainfall). This is 400mm in wet dry tropical northern Australia, 150mm in the colder and drier east and south, and 200mm in the west. There are some basic rules to the weather. Summer is HOT. Winter is mild. It doesn’t rain very often. It can rain at any time of year. It can also choose to rain regularly, or not at all. There are no averages. Sometimes no rain falls for years. Only in the wet dry tropics is there a wet and a dry season. Australia’s deserts are climactically capricious.This page contains climate information that is relevant to the southern half of Outback Australia including Eastern New South Wales, Northern South Australia, Eastern Western Australia, the southern regions of the Northern Territory, and Western Queensland. It also contains links to current weather information.
variations in wind patterns are controlled by shifts in the position of
the high-pressure belt (which forms part of the global sub-tropical ridge),
from the southern portions of the continent in summer to the latitudes of
central Australia in winter. During the warmer half of the year (October
March), the ridge is located in the south of the area; most of the
prevailing winds are from the southeast quadrant. During autumn the mean
position of the ridge moves north and remains over the centre of the continent
for the cooler months (April to September), and winds tend to be lighter.
Gale force winds (in excess of 61kph) are uncommon, being most frequent
from October to December when they are observed on average one day per month. In many parts of the outback Aboriginal people call this windy season.
variability in the Outback is among the highest in Australia, and average
annual totals are amongst the lowest. In effect there is no real seasonality.
The principle synoptic influences on rainfall are of tropical origin, taking
the form of moist tropical airmass incursions, rain and monsoon depressions
and thunderstorms. Even so, mid latitude influences together with frontal
activities produce rain. In other words, the tail ends of tropical cyclones
can come down from the north and deluge the country in summer, as can the
tips of cold frontal systems from the south in winter. The northern half
of South Australia lies on the northern or southern end of these systems,
and therefore is the driest place in Australia. The driest recorded place
in Australia is Mulka Station on the Birdsville Track, where rainfall is
below 120mm per annum.
is dependent on sunshine, temperature, humidity and wind, and is measured
as a potential value, assuming an unlimited water supply. Average evaporation
rates in the Outback are greater than 3,400 mm. In the Simpson Desert they
are estimated to be 3,800 4,000mm.
Drought refers to an acute water shortage. It implies that rainfall for
a given period is less than a certain threshold. In Oodnadatta, years with
rainfall in the first decile (ie. The lowest 10% of falls on record) since
1900 were 1900, 1915, 1918, 1928, 1929, 1934, 1937, 1940, 1944, 1951, 1959,
1960, 1961, 1965, 1967, 1970, 1972 and 1990.