Mountain landscapes have dynamic climates that, together with tectonic processes, importantly influence their topographic evolution. While spatio-temporal changes in rainfall are ubiquitous in these settings, their influence on river incision has been little studied. Here, we investigate how changes in rainfall pattern should affect both the steady state form and transient evolution of river profiles at the catchment scale using the stream power model. We find that non-uniform rainfall patterns complicate steady state relationships among conventional catchment-wide metrics like mean rainfall, channel steepness, and fluvial relief, which can influence the apparent sensitivity of landscapes and erosion rates to rainfall variations. We also find that transient responses to changes in rainfall pattern have an inherently multi-stage nature that importantly differs from expected responses to uniform changes in rainfall. This has several important implications, specifically for detecting transient responses to changes in rainfall pattern (and more broadly climate) in natural settings, and for interpretations of landscape morphometrics above and below transient knickpoints. We find that disparate responses by rivers and river segments that experience different rainfall conditions, particularly trunk and tributary rivers, are an important factor in understanding catchment-wide responses, and accounting for such disparities may be important for detecting and quantifying landscape sensitivity to rainfall variations. Lastly, we show how explicitly accounting for rainfall patterns in channel steepness calculations, and thus variations in erosional efficiency, may be a necessary step toward overcoming challenges related to rainfall variations, and thus ultimately for advancing understanding of landscape sensitivity to climate in mountain settings.