This paper supplements the existing climatic analyses for Darwin and the surrounding region, by providing a classification of years in terms of amount and distribution of rainfall, and highlighting the extreme, episodic rainfall events that have occurred in the period 1870 to 1983 inclusive. Approximately 77% of years have had significant departures from the two most frequent rainfall patterns and these are described. Much of the variation between years or groups of years lies in the dry and dry-wet transition periods. While the reliability of rainfall in the wet-dry tropics has been emphasized, rainfall variability over both the dry and wet seasons would seem to be an equally important characteristic, at least for the biota. In an environment such as the wet-dry tropics, where moisture is the primary limiting factor, rainfall variability has important implications for the design and interpretation of faunal and floristic surveys, monitoring programs and field experiments.