Because most Pacific mountain tributaries are situated in the Northern hemisphere, the runoff regime is characterized by high river flows in April-September and low river flows in October-March. With regard to global warming, a partial shift of inflows into the Pacific Ocean from the summer to the winter has to be expected. For quantitative evaluations, the SRM snowmelt runoff model is applied in several basins in the Pacific rim, ranging from 57° North (west coast of Canada) to 45° South (east coast of New Zealand). In the Kings River basin of California (4000 km₂, 171-4341 m a.s.l.) with the envisaged rise of temperature, runoff in October-March is significantly increased at the expense of snow accumulation in winter and summer runoff. Also, summer runoff peaks are shifted to earlier dates. Similar redistribution of runoff is evaluated for the Illecillewaet River basin of British Columbia (1155 km², 509-3150 m a.s.l.), a tributary to the Columbia River. However, an additional effect is observed: Because nearly 10% of the surface is covered with permanent snowfields and glaciers, runoff would be temporarily increased from these frozen reserves. A quantitative analysis reveals that in the Illecillewaet basin, even a moderate increase of precipitation would not offset a gradual disappearance of glaciers due to increased melting.