Average annual rainfall varies from at the edge of the Wheatbelt region to in the wettest areas near Northcliffe, the southwesternmost tip of Australia, but in the months of November to March, although rain still falls, evaporation exceeds rainfall and it is generally very dry. Plants must be adapted to this as well as the extreme poverty of all soils. A major reduction in rainfall has been observed, with a greater number of rainfall events in the summer months. The central four-fifths of the state is semi-arid or desert and is lightly inhabited with the only significant activity being mining. Annual rainfall averages about , most of which occurs in sporadic torrential falls related to cyclone events in summer months.