Western Australia’s climate is one of the most diverse in the country, varying greatly across the state’s expansive landscapes. The southwest coastal region enjoys a Mediterranean climate, characterized by mild, wet winters and hot, dry summers. This area, once heavily forested with towering karri trees, is renowned for its biodiversity. The region is home to one of the world’s most biodiverse terrestrial habitats, with a high proportion of endemic species, and thanks to the offshore Leeuwin Current, it is one of the world’s top six regions for marine biodiversity. It also boasts the southernmost coral reefs in the world.

Rainfall in this region varies, with the coastal areas receiving 300 millimeters (12 inches) of rain annually, while the wettest areas near Northcliffe can see up to 1,400 millimeters (55 inches) annually. However, from November to March, evaporation outpaces rainfall, leading to dry conditions for much of the year. The local plant life is well adapted to both the dry conditions and the nutrient-poor soils.

In stark contrast, the central two-thirds of Western Australia are arid, with the land sparsely populated and the only significant economic activity being mining. Annual rainfall in this region averages under 300 millimeters (8–10 inches), and most of it occurs in sporadic, intense downpours during cyclone events in summer. The extreme dryness and vast, empty landscapes make this part of the state one of the most challenging for both inhabitants and wildlife.

The northern tropical regions of Western Australia, particularly the Kimberley, experience a hot monsoonal climate. Average rainfall in this area ranges from 500 to 1,500 millimeters (20–60 inches) per year, but the region has a long dry season from April to November. Despite the abundance of runoff during heavy seasonal floods, the shallow, nutrient-poor soils restrict development to areas like the Ord River, where agricultural initiatives have taken root.

Snowfall is a rare occurrence in Western Australia, typically confined to the Stirling Range near Albany, the only mountain range in the state high enough and far enough south to experience snow. Snow can occasionally fall on the nearby Porongurup Range, but these events are infrequent and short-lived. The most significant low-level snowfall occurred on June 26, 1956, when snow was recorded as far north as Wongan Hills.

Western Australia is no stranger to extreme temperatures. The highest temperature recorded in the state was a scorching 50.7°C (123.3°F) in Onslow on January 13, 2022, while the coldest temperature, −7.2°C (19.0°F), was recorded at the Eyre Bird Observatory in August 2008. Additionally, the geomagnetic pole is tilted 10 degrees toward the state, making it one of the few places in the world where the aurora australis can be seen as far north as Geraldton.

Western Australia’s complex and varied climate plays a critical role in shaping the state’s ecosystems, agriculture, and the livelihoods of its residents, while presenting unique challenges for both environmental conservation and development.