New Zealand is perhaps most acutely vulnerable to the effects of climate change via extreme rainfall and its potential to cause significant flooding and landslide. Whilst the warming atmosphere can hold more moisture, potentially delivering more intense rainfall extremes, New Zealand’s situation as a steep isolated landmass in the path of strong westerly winds means the effects of circulation changes are also important, and they can sometimes counteract the intensification signal. Significant geographical variations exist in New Zealand rainfall and its extremes. The ‘weather@home ANZ’ model (HadRM3P nested in HadAM3P) is shown to be capable of reproducing these variations with a good degree of accuracy, and is evaluated here by comparison with observations from ‘HIRDS’ (High Intensity Rainfall Design System), New Zealand’s foremost tool for infrastructure planning related to heavy rainfall. Strong W-E contrasts in extreme rainfall, particularly across the Southern Alps, are modelled well, as are regions of high rainfall associated with high elevation elsewhere. Large ensembles (order 2000 members) of simulations of this model have been created for end-of-century conditions under both 1.5 and 2 degrees of warming, as part of the ‘HAPPI’ (Half a degree Additional warming: Prognosis and Projected Impacts) modelling framework. These reveal that similar geographical patterns are evident in projected changes to extreme rainfall, with a W-E pattern indicating wetter extremes in the west and drier in the east. Expressed as percentage changes from current conditions, the projected reductions in extreme rainfall in the east often exceed the projected increases in the west in magnitude. Taken together with previous research on attributable changes to date, the picture of projected changes in extreme rainfall will, it is hoped, contribute valuable information for those planning for adaptation to New Zealand’s coming climate changes.