The Kimberley has a strongly arid to semi-arid monsoonal climate that is characteristically hot and wet in the summer (wet season) and warm and dry in the winter (dry season). The months of May to August are relatively cool with average temperatures between 16°C and 32°C. In the remaining months maximum temperatures exceed 35°C and in October-November often exceed 38°C.
Annual average rainfall ranges from 1,500 mm in the north-west coastal areas to less than 350 mm on the southern perimeter and is generally confined to the six-month ‘wet’ period November to April, with January and February being the wettest months. It has a pronounced north-south rainfall gradient, so that southern parts of the zone are semi-arid, with a shorter growing season, less reliable rainfall and higher annual temperature range than the northern parts.
The Kimberley includes over one hundred rivers and many more creeks and streams which flow north or west, forming the Timor Sea drainage division.They exhibit highly seasonal flow conditions as a result of being located at the southern edge of the global monsoon system, where intense and widespread rainfall results in flood flows during summer.The largest river in terms of flow in the Kimberley, and in WA, is the Fitzroy – which has floodplains several kilometres wide. The Ord is the second largest river in WA and one of the most well known. Water from the Ord River is used in the economically important Ord River Irrigation Area.
There are 23 wetlands (including rivers) of national importance and four Ramsar listed wetlands within the Kimberley and nine on the Register of National Estate. The four declared Ramsar sites (listed as International wetlands of significance under a global treaty) in the Kimberley are Lake Kununurra and Lake Argyle, the Ord River Floodplain, Roebuck Bay and Eighty Mile Beach. Paruku (Lake Gregory) also satisfies criteria for listing as a Ramsar site.
The Kimberley coast is approximately 2,500 kilometres in length and contains more than 3,000 islands. It's unique from an Australian perspective due to its large tidal range, with a movement of up to 12 metres driving coastal processes.
This coast is one of the most contorted of anywhere on the Australian coastline and its geological, biological and anthropogenic history is unique.
Flora and Fauna
Biodiversity in this subregion is unique and highly varied. It supports a diverse and spectacular flora of more than 2000 plant species and the fauna is unique and rich in species diversity, including many threatened and endangered species.
Vegetation is generally characterised as tropical savanna, although there is considerable variation throughout, determined by rainfall, topography and soils. The most extensive vegetation is eucalypt woodland and open woodland, but there are also areas of hummock grassland, tussock grassland and acacia open woodland. The ground layer is almost always dominated by grasses, with grazing mostly based on native, perennial tussock grasses and in some instances introduced buffel and birdwood grasses.
The Kimberley contains five IBRA sub-regions: Central Kimberley, Dampierland, Northern Kimberley, Ord Victoria Plains and Victoria Bonaparte. To read more about IBRA subregions, and to access the Australian Government's detailed descriptions of each, see the IBRA subregions page.