The Pilbara has a semi-arid to arid climate that is characterised by high temperatures, low and variable rainfall and high evaporation. Between the months of October and April temperatures exceed or reach 32°C almost every day and the average maximum temperature is often over 40°C. In the winter months the average temperature falls to 25°C. Inland the temperatures are generally higher due to the absence of a cooling sea breeze.
The average annual rainfall of the Pilbara subregion ranges from about 200 to 350 mm per year, however, the rainfall can vary widely from year to year. Most of the rain falls in the summer months between December and March but can continue through until June. This is followed by a pronounced dry period between August and November. The average yearly evaporation is about 2,500 mm; this exceeds the average yearly rainfall and is consistent throughout the year.
The coast from Port Hedland to Exmouth Gulf is the most cyclone prone area in Australia, with three to four tropical cyclones expected every year.
The major river systems of the Pilbara are the Fortescue System, and the De Grey and Lesser rivers off the Northern divide of the Chichester Range. Along many of the region's rivers e.g. the Fortescue and Oakover rivers, rock holes, gorges, grassy floodplains and wooded riparian areas occur. Intermittent systems like the Fortescue and Oakover rivers drain the Hamersley Ranges, the largest mountain range in Western Australia.
Six Pilbara wetlands have been identified as being of national significance, for example, Fortescue Marsh and Millstream Pools. A further 12 have been identified as being of regional significance.
The Pilbara coastline is characterised by deltas like the De Grey River delta, barrier islands and lagoons with extensive mangroves, wide tidal mudflats like the Roebourne Plains and long stretches of sandy beaches or rocky shorelines.
The Dampier Archipelago has pristine reefs with islands that are virtually untouched. Some of the marine areas within the region, like the Dampier Archipelago, are considered to be the most biologically diverse in the state.
Flora and Fauna
The Department of Environment and Heritage identified the Hamersley-Pilbara area as one of the 15 biodiversity hotspots of Australia. This region provides habitat for a number of threatened, endemic and fire sensitive species and communities e.g. the ghost bat, mulgara and spectacled hare-wallaby.
This Pilbara contains one threatened ecological community, 2 species of Declared Rare Flora (DRF), 30 Priority One Flora, 23 Priority 2 Flora, 7 Schedule One mammals, 2 Schedule One birds, 1 Schedule One reptile and 5 Schedule Four Fauna.
The Pilbara has one Ramsar listed wetland site which is located on the very southern edge of Eighty Mile Beach, as well as 15 wetlands of national significance, 33 wetlands of subregional significance and aquifers that support endemic stygofauna.
Arid grasses and shrubs are found widely throughout the Pilbara subregion. Hummock grasslands are the most extensive vegetation type; as well there are significant areas of tussock grassland, acacia woodland and open woodland. Smaller areas of chenopod shrubland and eucalypt woodland occur primarily on floodplains and along drainage lines. The coastal strip consists of grasslands and low open woodlands and the coastal flats have mangroves scrub.
The Pilbara contains one IBRA sub-region, named Pilbara. To read more about IBRA subregions, and to access the Australian Government's detailed descriptions of each, see the IBRA subregions page.