The Arid Continent
With much of Australia lying between 20° and 30° south, combined with such a large land mass, it isn't surprising that the country has its fair share of deserts. In fact Australia is the driest continent on earth with approximately 70% of its area termed arid or semi arid. The most arid parts of Australia are the western and central parts of the continent and other than a few coastal patches to the north, east and south, the rest of Australia is termed semi-arid.
While Central Australia is a dry place, it certainly does rain. Alice Springs gets about 275 mm of rain a year falling mainly between October and March. The average rainfall decreases as you move south with the Lake Eyre basin receiving about 100 – 140 mm per year. Alice Springs, sitting at the base of the MacDonnell Ranges, actually has higher average rainfall and slightly lower average temperatures than the rest of Central Australia due to the higher altitude.
Most rain in Central Australia is the result of summer monsoon activity that brings large volumes of rain to northern Australia as well as tropical cyclones that originate off the north-west coast. In both instances it is the frequency and degree that the monsoon troughs or cyclones penetrate south and inland that determine the amount of rain that falls. Luckily it is the predominantly flat terrain that allows these events to happen with the frequency that they do as there are no mountain ranges to block the moisture from the north and north-west.
Feast and Famine
Like most desert regions, rainfall and temperatures can vary greatly. It is not uncommon for an average year's rainfall to occur in a single month and sometimes, in a single day. From 1973 – 1976 was a particularly wet period where parts of Central Australia received double their average rainfall over the 4 year period. Lake Eyre filled up, which is very rare, as well as widespread flooding throughout the interior. Between 1999 and 2001 was another very wet period with some locations getting nearly 3 times their normal rainfall. Conversely, there are times of sustained dry periods such as the "Federation Drought" that occurred between 1895 and 1903 that led many pastoralists to abandon their stations.
Without wanting to state the obvious, summers are very hot in Central Australia. The average maximum temperature is over 35° in December, January and February but it is quite common for temperatures to go over 40°, but unlikely to exceed 45°. Cloudless days and dry air cause large ranges in temperature between night and day, often as much as 20°. Below average summer daytime temperatures are usually associated with rain activity.
What many visitors to Central Australia often don’t realise is that temperatures in winter, particularly overnight, can be very cold with morning frosts quite common. The lowest recorded minimum was -7.5° which happened in 1976 and the lowest maximum 7° in the same year. Daytime temperatures in June and July can go up to around 20° but with the shorter daylight hours, don't stay there for very long. If the wind blows from the south-east there can be quite a severe wind chill factor. There have even been instances of snow in a few areas with snow falling on Uluru (Ayers Rock) in July 1997.
When travelling into Central Australia it is worth remembering that like most desert regions, they are subject to quite dramatic variances from the norm so it is best to be well prepared, particularly in winter with plenty of warm clothing.