Cold southern airflows, wedging beneath humid north westerly winds triggers vertical instabilities, bringing this region the bulk of its rain between May and August.

During the summer months these frontal depressions travel well to the south, leading to warm high pressure systems dominating the southern part of the state.

Between April and October the climate is characterised by dry months with clear blue skies, moderate daytime temperatures and cool nights.

On close to the centre of the Western Australian border Giles Meteorological Station records only 219 mm of rain over an average of 43 days.

Inland the river gorges are inclined to flash flooding with the occasional sudden downpours, giving sufficient water for sheep and cattle stations.

The state is generally snow free throughout winter, although an occasional fall is reported once or twice a year on the Stirlings or Porongurups north of Albany (837 mm over 179 days).

As a result, the figures that suggest that 1/3 of Western Australians will in the course of their life suffer from skin cancers, has caused a huge change in popular behavior.

From being a part of a nation of sun-loving beach-goers, Western Australians have adopted a habit of "slipping" on a shirt, "slopping" on a 15+ sunscreen and "slapping" on a hat.

The increase in numbers of blind kangaroo suffering from ultraviolet caused cataracts has been recorded in local newspapers, but the overall effects has not been studied.

[4] The International Panel on Climate Change has shown that the natural ecosystems can absorb approximately two tonnes of carbon dioxide per person per year.

The gently undulating landscape of low relief has Proteaceous scrub-heaths, rich in endemics, on residual lateritic uplands and derived sandplains; mixed eucalypt, Allocasuarina huegeliana and Jam-York Gum woodlands on Quaternary alluvials and eluvials.

The Limestone strata are covered with Acacia startii and binervia shrublands outcrop in the north, where extensive tidal flats in sheltered embayments support Mangal vegetation.

Diverse woodlands rich are in K strategy endemic eucalypts, on low greenstone hills, valley alluvials and broad plains of calcareous earths.

Mixed shrub steppe of Acacia, Hakea and Grevillea over Triodia pungens occurs on red sand plains and dune fields.

Vegetation is mainly of proteaceous scrub-heaths, rich in endemics, on the sandy earths of an extensive, undulating, lateritic sandplain mantling Permian to Cretaceous strata.

It comprises open hummock grassland of Triodia pungens and Plectrachne schinzii with scattered trees of Owenia reticulata and Bloodwoods, and shrubs of Acacia species, Grevillea wickhamii and Grevillea refracta, on Quaternary red longitudinal sand dune fields overlying Jurassic and Cretaceous sandstones of the Canning, Centralian, Arunta and Armadeus Basins.

Gently undulating lateritised uplands support shrub steppe such as Acacia pachycarpa shrublands over Triodia pungens hummock grass.

The Little Sandy Desert In this region red Quaternary dune fields have abrupt Proterozoic sandstone ranges of Bangemall Basin.

Sparse shrub-steppe is found over Triodia basedowii on stony hills, with River Gum communities and bunch grasslands on alluvial deposits in and associated with ranges.

A mosaic of mixed eucalypt woodlands and mallee occurs on calcareous earth plains and sandplains overlying Eocene limestone strata in the east.

The Murchison This arid region of Mulga low woodlands, is often rich in ephemerals, on outcrop hardpan washplains and fine-textured Quaternary alluvial and eluvial surfaces mantling granitic and greenstone strata of the northern part of the Yilgarn Craton.

The sandplains support mixed shrub steppes of Hakea suberea, desert bloodwoods, acacias and grevilleas over Triodia pungens hummock grasslands.

Plateaux and abrupt ranges of Proterozoic sandstone, known as the Victoria Plateau, occur in the south and east, and are partially mantled by skeletal sandy soils with low tree savannas and hummock grasslands.

Mulga, Callitris- Eucalyptus salubris, and Bowgada open woodlands and scrubs on earth to sandy-earth plains in the western Yilgarn Craton.

[17] It is a frequently repeated commonplace of Australian historiography that the eastern border of Western Australia at 129° East derives from the 1494 Treaty of Tordesillas between John II of Portugal and Ferdinand and Isabella of Spain.

Under the Iberian Union later in the century, the Spanish did not redeem or annul the treaty and the Portuguese continued to administer their separate territories; however, their maps began to use a demarcation line further west at 135° E.[27] The Dutch, British, and French never respected any of these lines as generally binding,[28] but in 1664 the French author Melchisédech Thévenot—apparently on his own initiative[29]—published Abel Tasman's 1644 map of Australia,[30] "correcting" the placement of Tasman's latitudinal scale to create a division between New Holland (Dutch by right of conquest after the fall of Malacca and the Portuguese East Indies)[28] and a Terre Australe ("Southern Land") to its east, only partially claimed in the area of "Austrialia" where Pedro Fernández de Quirós had landed in 1606.

In 1786, the British then declared it to be the western boundary of New South Wales[28] finding it convenient to ignore Dutch claims to the entire continent as they attempted to forestall potential French expansion and to replace America as a penal colony.

[31][page needed] The line was later moved west to 129° E. in 1825 solely to adequately cover the short-lived settlements at Port Essington and Fort Dundas.

[35] Stirling and the Swan River Company settled three easily defensible sites: Perth as their capital, Fremantle as their port, and Guildford as their agricultural centre.

Thus Albany Highway crossed the river at the fords of Matta Garrup ("Leg-Deep Place", now the Causeway), going south to Thomas Peel's lands along the Murray in Pinjareb country.