South Australia
Climate and Weather
The climate of South Australia has frequently been described as a ‘Mediterranean’ type with mild wet winters and hot dry summers. In fact, this description can be applied only to the southern settled districts which are subject to seasonal shifts in weather influences deriving from the continental interior to the north and the Southern Ocean to the south.
The dominant weather features are the eastward moving high and low pressure systems and the seasonally varying northerly continental and tropical influences. Although there is popular recognition of four seasons, the principal seasonal contrasts are warm-to-hot, dry summers and cool-to-mild winters. The highest rainfall occurs along the southern coasts and the Mount Lofty Ranges (with an average annual rainfall of 1200 mm in the vicinity of Mount Lofty); the lowest rainfall occurs in the region of Lake Eyre where the average annual totals are less than 150mm.
Most of the rain in the southern districts of the State falls during the winter months when the sub-tropical high-pressure belt is displaced to the north over the Australian continent. Migratory lower-pressure systems are thus able to extend further to the north, allowing strong cold-frontal activity to penetrate across the southern settle areas. A two-to-three-day cycle of easterly moving high and low pressure systems is a familiar weather pattern in Southern Australia.
During the summer months of December to March, the subtropical high-pressure belt is displaced to the south of the continent, and frontal activity results in northerly to south to south-east wind changes, or summer ‘cool changes’, with little or no rain. Summer rainfall is generally low over the State. Occasionally, however, unstable ‘moist infeed’ at middle to lower levels of the atmosphere from the north-east or north-west, associated with tropical weather systems over northern Australia, can produce thunderstorms and heavy rainfall in the north of the State. Very heavy summer falls in the north are often caused by incursions of the summer monsoon trough and/or rain depressions which are generally the remnants of tropical cyclones. More locally, the orographic influence of the Flinders Ranges can be decisive in some of these situations.
