The InterTropical Convergence Zone (ITCZ) delivers intense precipitation for the tropical regions of the globe. The Australian tropics receives ~80% of its annual mean rainfall in the wet season (November-April), influenced by the arrival of the Australian Summer Monsoon (ASM) as the ITCZ moves south of the equator. Northern Australian rainfall projections are uncertain due to a paucity in understanding the ITCZ dynamics, the ITCZ/ASM relationship, and the large internal variability of these climatic phenomena. This study explores Central-Indo-Pacific (CIP) ITCZ dynamics, using a new set of indices that better capture the ITCZ intensity, latitudinal width, centre and southern edge positions (S_edge); and by using the Sr/Ca record measured in a speleothem collected from Katherine, Northern Territory, Australia. Over the instrumental period, increases in ASM intensity and rainfall are correlated with southward latitudinal movements of the southern ITCZ edge (r = -0.71, -0.73 respectively, p < 0.01). The southern edge is a function of ITCZ position and width, highlighting the problems with linking changes in paleo-ASM rainfall to latitudinal ITCZ movements alone. The southern ITCZ edge position is dominated by 3-year interannual variance, punctuated by shorter periods of ~7-year variance, over the instrumental period. The Sr/Ca records, covering ~1429-1478, ~1761-1777, ~1851-1870 and ~1885-1933, show robust seasonal signals modulated by hydrological change that also reflect S_edge and the dominance of 3- and 7-year periodicities. The 3-year cycling brings more intense rainfall totals and seasonality to the northern Australian region relative to the 7-year frequency, but longer Sr/Ca records are needed to assess their drivers.